Roundup: the Radeon HD 7970s and 7950s from Asus, HIS, MSI, PowerColor, Sapphire and XFX - BeHardware
>> Graphics cards

Written by Damien Triolet

Published on October 26, 2012

URL: http://www.behardware.com/art/lire/853/


Page 1

Introduction



How good are the customised Radeon HD 7970s and 7950s? To give an answer to this question, we have looked in detail at the Asus, HIS, MSI, PowerColor, Sapphire and XFX releases as well as the reference cards. When heat, noise and overclocking are all taken into account, which one is the best Radeon HD 7900?


Numerous variants, out rapidly
Quite unusually for high end graphics cards, the customised models from AMDís partners came onto the market very quickly, some even arriving at launch of the cards, notably the XFX Radeon 7970 Double Dissipation Edition, though of course this card is based on the reference PCB. Asus was the first to customise the Radeon HD 7970 entirely with the DirectCU II model, with the competition hot on its heels.

AMD actually produced two reference models of the Radeon HD 7950. The first, derived from the Radeon HD 7970, seems to have been reserved for the press and the second made available to the different graphics card manufacturers as a base model from which to come up with their own designs.

A graphics card can be customised either with a new cooling system or a new PCB or both at the same time. On most of the Radeon 7950s available at launch, the manufacturers have used the reference PCB (different to the press release) made in the factory of their choice with components of their choice (but which of course follow certain criteria) and have settled for modifying only the cooling system.

Customising the cooling system allows them to differentiate their cards or try to reduce somewhat their costs in comparison to the reference cooler which may be relatively costly. To keep production costs down on their high end in-house variants, the biggest manufacturers have elaborated more or less generic cooling systems that they can roll out on the maximum number of models, allowing them to benefit from an economy of scale in terms of production and R&D costs.

It's not all about the cooling system however, notably with the Radeon HD 7900s which have a very high margin for overclocking calling for a sufficiently sturdy power stage to make the overclocking potential fully exploitable. We will be checking to see if the power stages used are solid enough, particularly on the Radeon HD 7950s on which a second reference PCB optimised for cost reduction has been used by numerous manufacturers.

In this test we will concentrate on comparing the different Radeon HD 7900s between themselves. For more details on performance in comparison to the competition, we invite you to consult the reports dedicated to such comparisons: Radeon HD 7970 and Radeon HD 7950.

Hereís the list of the cards tested. This will be added to as new models reach us:

AMD Radeon HD 7950 press edition
Reference AMD Radeon HD 7970
Asus Radeon HD 7970 DirectCU II TOP
HIS Radeon HD 7950
MSI Radeon HD 7950 Twin Frozr III
MSI Radeon HD 7970 Lightning
PowerColor Radeon HD 7950 PCS+
Sapphire Radeon HD 7950
Sapphire Radeon HD 7950 OverClock
XFX Radeon HD 7950 Black Edition Double Dissipation
XFX Radeon HD 7970 Double Dissipation


Defective test samples
Before getting further into the report, we canít but mention the many problems weíve had that have contributed to delaying it: defective fan fixtures, screws that have fallen off into our hands on removing cards from their packaging, insufficient coolers pressure against the GPU, changing of biosí and so on. Some of the press samples seem to have been assembled slap dash before the employees of the different factories headed for the hills for the Chinese New Year. We certainly hope that more attention is given to the cards on sale in stores!

Although we were able to resolve most of these issues, sometimes with a second sample card that had been corrected, we still havenít been able to test the Asus Radeon HD 7950 DirectCU II. The fixture system, such as the one on the first sample model, doesnít exert enough pressure on the GPU and one of the four screws doesnít have any purchase on anything. You can imagine what might happen when the card is placed horizontally in a casing... If you don't, here is what we noticed with the press sample as well as a commercial sample : GPU overheating.

On one hand Asus has recognised the issue, which can be rectified simply by adding a washer to the screw (moreover, this is what all the other manufacturers have done, AMD's spec probably not proving sufficiently precise originally), but on the other Asus Taiwan is dragging its feet in terms of confirming that the first available cards in stores wonít suffer from this problem. As things stand, we therefore advise you to avoid this model. Our current interpretation is that the manufacturer has slightly modified its production procedure for this card, or is currently doing so, to make sure the cooler fixture functions properly but does not intend to admit to the fault on the first shipments, safe in the knowledge that the issue wonít cause an immediate crash on every sample.


Page 2
Test protocol 2.0

Test protocol 2.0
After two and a half years of loyal service, we have decided to pension the Sonata 3 off as well as the first version of our full test protocol given over to measuring the thermal characteristics of graphics cards. Over the years we have looked in detail at no fewer than thirty-seven graphics solutions, thanks in particular to thermal imaging and this formed a useful database, giving us the ability to position the results of new solutions objectively.

Test protocol 2.0 has also been designed to be used for a while. Here we use a Cooler Master RC-690 II Advanced casing, which is radically different to the Sonata 3. With many perforations, itís also better equipped cooler wise, with a 140 mm suction fan at the front and 120 mm and 140 mm extraction fans at the back in place of the single 120 mm fan on the Sonata 3.
We have also modified it slightly by replacing the original set of fans with Noctua models: an NF-P14FLX to suck air in and two NF-S12Bs for extraction. This modification improves the cooling to noise ratio and above all removes the mechanical noise you get with the original fans. Although this noise didnít alter the noise pressure obtained during readings by much, it did make it difficult to register noise levels by ear, which is important when the graphics card fan is also producing a mechanical noise or when its speed varies.


Instead of the X48 and Q6600, weíre now on a P67 and Core i7-2600 platform. We went for the Asus Sabertooth P67 motherboard which has an additional slot between the CPU and the first graphics port, making it easier to take infrared photos. We did however remove its plastic protection which was stopping us from viewing the temperature of various areas of the PCB. While we previously used the Intel cooler box, here we went for a Big Shuriken from Scythe, which is more effective and isnít subject to the size issues you get with tower models (again a problem when taking the photos).

We used a Scythe Kaze Master rheobus to control the speed of the CPU and case fans. The CPU fan was thus fixed at 900 RPM both at idle and in load. The Noctua fans run at 600 RPM in idle, while in load the 140 mm ups its speed to 780 RPM and the 120 mm to 990 RPM.

We opted for a high-end power supply: the Seasonic X850. It has the advantage of being passive when energy consumption is under 200W, namely when our system is at idle. We used an OCZ Vertex 2 64 GB for the system disk and two hard drives, a Hitachi Deskstar 7200 RPM and a Western Digital Raptor 10000RPM, as secondary drives.

Thanks go to Asus, Cooler Master, Intel and Seasonic for supplying most of the components required for setting this test system up.

We kept our Fluke Ti25 thermal camera for the readings, which gives us an image of the different temperatures that we also took using the sensors on the Asus Sabertooth. However we did replace our sonometers with the Cirrus Optimus CR152A Class 2 models that allow us to measure sound levels down to 21 dBA, which is as low as the room allows us to go. The noise level readings are not therefore comparable with the old ones, which went down to a minimum of 35 dBA.


The sonometer was mounted on a base and placed 50 cm from the side of the casing, raised up 20 cm from the table on which the casing was placed. The solutions measured at between 21 and 22 dBA can be considered as silent. Up to 25 dBA and the cooling is very discreet. Between 25 and 30 dBA can be seen as discreet. Between 30 and 35 dBA can be seen as standard and between 35 and 40 dBA is starting to get noisy. Anything higher than this is noisy and can become excessive for a computer, though of course, as with the other thresholds, this is subjective and depends on several factors such as the regularity of the noise and the environment.

This time we decided to measure the noise levels both during standard usage of the casing and with the graphics card isolated, turning the hard drives and CPU and casing fans off. This allowed us to differentiate between the least noisy cards in much more detail.

The load test has also moved on. We have replaced the 3DMark06/07 Pixel Shader test, in which fps values went much too high, with the first scene from 3DMark 11. We opted for this one because it doesnít use tessellation, a rendering technique that could lead to a drop in energy consumption on cards that suffer from a bottleneck at this level. This scene is however 5% less demanding in terms of energy consumption than that in 3DMark06, which worked the texturing units a good deal more. This load test is therefore now very similar to a very demanding game and a good deal different to tests such as Furmark and OCCT in terms of energy consumption. The CPU was loaded with Prime95 on 4 threads, with the lowest priority.

Hereís how we organised the tests:

- Ambient temperature reading to keep it between 25 and 26įC
- 45 minutes at idle
- Noise level reading
- Temperature sensor readings
- Casing is opened rapidly for thermal imaging photo
- Casing is closed
- 45 minutes in load
- Noise level reading
- Casing is opened rapidly for thermal imaging photo
- Casing is closed
- Temperature sensor reading via log
- 45 minutes in load with overclocking
- Noise level reading
- Casing is opened rapidly for thermal imaging photo
- Casing is closed and two hard drives turned off
- GPU temperature sensor reading via log
- CPU and casing fans switched off
- Speed of GPU fan fixed manually to idle/load/overclocking/100% and noise reading taken.

Note that with these last readings we made sure the RPMs were identical and not only the speed expressed as a %, as they can vary slightly with the voltage supply to the fan when the GPU is in load.

Lastly, the readings taken during overclocking were taken pushing the card as far as it would go, including a modification of the GPU voltage as well as memory overclocking.


Page 3
Review: AMD Radeon HD 7950 press edition

The Radeon HD 7950 press edition
On launch of the Radeon HD 7950, AMD supplied us with a Ďreferenceí Radeon HD 7950 based on the same design as the reference Radeon HD 7970. There is however a second reference model, equipped with an axial fan and a revised, lower cost PCB. This is the reference model that youíll find in stores from certain partners. To our knowledge, the card supplied to us by AMD will not be put on sale and is therefore not representative of the final product that youíll find in stores. This isnĎt the first time that AMD have tried such a manoeuvre, which is regrettable. For information however, hereís what this test sample gives:

The card



This Radeon HD 7950 is based on the reference design of the Radeon HD 7970 which in turn is in the same format as the reference Radeon HD 6900: double slot and 27.5 cm long. The cooling system has however changed slightly in comparison to the previous cards. The blower has longer blades to increase the airspeed and the vapour chamber block / radiator extends 1.5 cm further towards the connectors. Its extremity is therefore very close to the hot air extraction grill which has also been adapted to cover the height of a PCI slot.

Itís therefore no longer necessary to send some of this hot air into the casing above the card though one of the two DVI ports has had to go, with the remaining one accompanied by an HDMI out and two mini-DisplayPort outs. An HDMI to DVI adaptor is supplied with the card.

Probably to reduce costs, AMD has not continued to use the plate that covered the back of the Radeon HD 6970 and 6950 2 GB models. The design of the casing that covers the cooling system has however been modified to make it much more aesthetic than the one used for the Radeon HD 6900s, which had a rather austere look and a cheap feel. In general, weíre not great fans of glossy designs but here it has been carefully made with quality materials.


The PCB is not that different to the one used for the Radeon HD 6970, but the power stage has been revisited to make it more powerful, with better quality components though still with 6 phases for the GPU. The Radeon HD 7950 makes do with four of these phases for a TDP of 200W. The design will however allow manufacturers who so desire to produce an overclocked model with more in reserve and it will also be possible to move to a 2x8 pin power supply connector set-up as against 2x 6 pin for the Radeon HD 7950 press edition.

The Radeon HD 7950 uses Hynix T2C GDDR5 memory certified at 1.25 GHz, as well as two biosí which you can select between using a small switch. By default one of the two biosí is protected during writes and therefore serves as a backup, for example during overclocking via the bios.


Overclocking, undervolting and energy consumption
Here are the various configurations we were able to obtain with the Radeon HD 7950 press edition (GPU clock / memory clock @ GPU voltage):

800 / 1250 MHz @ 0.900V: 110W
800 / 1250 MHz @ 1.093V: 154W (by default)
1050 / 1525 MHz @ 1.093V: 191W
1125 / 1525 MHz @ 1.150V
1150 / 1525 MHz @ 1.200V
1175 / 1525 MHz @ 1.225V: 272W

During extreme overclocking, with a modified GPU voltage, the energy consumption of our test card increased by 77%. There's no need to tell you that the power stage suffers under these conditions!

Whatís more, the card then consumes more than 6.5A via the 12V connection on the PCI Express port, which could damage some motherboards as the standard is defined at 5.5A. It looks as if this PCB may well actually be poorly adapted to a 6+6 pin power supply, meaning it asks a lot more from the PCI Express port than the Radeon HD 7970 which uses an 8+6 pin type connector configuration.


Infrared thermography

[ At idle ]  [ In load ]  [ Overclocking ]


[ At idle ]  [ In load ]

The card is well cooled both in load and at idle. Once it has been overclocked its power stage may however heat up a lot as a result of the jump in energy consumption and the fact that itís limited to 4 phases.


Temperature and noise readings

As it has a blower fan most of the hot air generated by the card is expelled from the casing. Noise levels are lower than those for the reference Radeon HD 7970 as the GPU is less demanding. Nevertheless the card is still noisy in load and significant overclocking takes noise to a level that's difficult to put up with.

The RPMs as a % of the fan speed are as follows:

20%: 980 RPM
41%: 2175 RPM
59%: 3350 RPM
100%: 5335 RPM


Our opinion
Overall this Radeon HD 7950 is pretty effective, even if it hasnít really been designed to make the most of the Tahiti GPUís overclocking potential. In any case, little matter as this is a limited edition model, made for the press only. We donít expect it to turn up in stores, which is a shame as some configurations would benefit from this blower type design.


Page 4
Review: Reference AMD Radeon HD 7970

The reference Radeon HD 7970
For the launch of the Radeon HD 7970, AMD supplied us with a reference card that many partners immediately put on sale as it was, at the base clocks of 925 MHz for the GPU and 1375 MHz for the memory, or overclocked (in italics in the list) with the GPU up to 1 GHz:

Asus Radeon EAH7970 3GD5
Club 3D Radeon HD 7970 3 GB
Gigabyte Radeon HD 7970 3 GB
HIS Radeon HD 7970 3 GB
MSI Radeon R7970-2PMD3GD5
PowerColor Radeon HD 7970 3 GB
Sapphire Radeon HD 7970 3 GB
XFX Radeon HD 7970 3 GB Core Edition
XFX Radeon HD 7970 3 GB Black Edition


The card




The reference Radeon HD 7970 is in the same format as the Radeon HD 6970: double slot and 27.5 cm long. Its cooling system is similar but has been developed slightly. The blower has longer blades to increase the airspeed and the vapour chamber block / radiator extends 1.5 cm further towards the connectors. Its extremity is therefore very close to the hot air extraction grill which has also been adapted to cover the height of a PCI slot.

Itís therefore no longer necessary to send some of this hot air into the casing above the card though one of the two DVI ports has had to go, with the remaining one accompanied by an HDMI out and two mini-DisplayPort outs. An HDMI to DVI adaptor is supplied with the card.

Probably to reduce costs, AMD has not continued to use the plate that covered the back of the Radeon HD 6970 and 6950 2 GB models. The design of the casing that covers the cooling system has however been modified to make it much more aesthetic than the one used for the Radeon HD 6900s, which had a rather austere look and a cheap feel. In general, weíre not great fans of glossy designs but this one has been carefully made with quality materials.


The PCB is not that different to the one used for the Radeon HD 6970, but the power stage has been revisited to make it more powerful, with better quality components though still with 6 phases for the GPU. The Radeon HD 7970 makes do with five of these phases for a TDP of 250W. The design will however allow manufacturers who so desire to produce an overclocked model with more in reserve and it will also be possible to move to a 2x8 pin power supply connector set-up compared to 8+6 pin connectors for the reference Radeon HD 7970.

The Radeon HD 7970 uses Hynix R0C GDDR5 memory certified at 1.5 GHz, as well as two biosí which you can select between using a small switch. By default one of the two biosí is protected during writes and therefore serves as a backup, for example during overclocking via the bios.


Overclocking, undervolting and energy consomption
Here are the various configurations we were able to obtain with the reference Radeon HD 7970 (GPU clock / memory clock @ GPU voltage):

925 / 1375 MHz @ 1.025V: 146W
925 / 1375 MHz @ 1.174V: 187W (by default)
1075 / 1650 MHz @ 1.174V: 215W
1100 / 1650 MHz @ 1.225V
1125 / 1650 MHz @ 1.250V: 255W

Increasing the GPU voltage gains us 50 MHzÖ and 40W. On the other hand, reducing the GPU voltage also regains these 40W and reduces noise levels.


Infrared thermography

[ At idle ]  [ In load ]  [ Overclocking ]


[ At idle ]  [ In load ]

The reference Radeon HD 7970 is well cooled.


Temperature and noise readings

The readings confirm that the card expels most of the hot air from the casing. While the card is pretty discreet at idle, it does become noisy in load and very noisy once it has been overclocked.

The RPMs as a % of the fan speed are as follows:

20%: 1070 RPM
47%: 2550 RPM
54%: 3025 RPM
100%: 5340 RPM


Our opinion
The reference Radeon HD 7970 aims to keep the GPU temperature down by sending the hot air out of the casing. This design will above all suit compact or poorly ventilated casings, especially in the case of CrossFire X systems. However, if you have a well-aired casing youíre better off going for a model that isn't as noisy in load.


Page 5
Review: Asus Radeon HD 7970 DirectCU II TOP

Asus HD 7970 DirectCU II TOP
With the Radeon HD 7970 DirectCU II, Asus has given us the first fully customised Radeon HD 7970, all their own work, from the PCB to the cooling system. Itís available in a standard version, at the reference clocks, as well as in a TOP version, with the GPU overclocked to 1 GHz and the memory to 1.4 GHz:

Asus Radeon HD 7970 3 GB DirectCU II
Asus Radeon HD 7970 3 GB DirectCU II TOP

Asus supplied us with a TOP version of the card.


The card





As usual, the DirectCU II system makes the card very big with its triple slot format. While, at 27.5 cm, itís the same length as the reference Radeon HD 7970 (the PCB is a little longer but the cooling system doesnít stick out), it's 2.5 cm higher because of the cooler (the PCB is only 1 cm higher).

Six 6 mm heatpipes run over the DirectCU II system and then are shared across the two big radiators assymetrically: 4 for one and 2 + the base for the other. Two metal frames ensure overall robustness, one giving support to the two large 10 cm fans and the other in contact with the memory modules and sensitive power stage components (with an integrated radiator on top of them). A metal cover closes the card and channels the flow of air towards the radiators.

Finally, thereís a perforated metal plate at the back of the card but it isnít in contact with the PCB or other components. It doesnít therefore serve any cooling purpose but is there rather for aesthetic reasons as well as to protect the back of the PCB. Overall, the card's very well finished and inspires confidence with its solidity.

Asus has revisited the reference connectivity to give us two DVI outs as well as four DisplayPort outs. They are however limited by the fact that the second DVI out and the fourth DisplayPort out share some resources, though we donít know why as in principle there isnít any such GPU limitation. The small switch that allows you to switch from one bios to another is used here to configure these two outs: either the last DisplayPort is deactivated or the second DVI out is limited to single link (1920x1200 60 Hz). Note however that our test model, as well as a second model, refused to display anything on our 30" screen from both DVI connectors, whatever the position of the switch: corrupted display as of the bios for the second DVI out and black screen once the driver was loaded on both DVI outs. We therefore used a dual-link active adaptor from DisplayPort. This bug should be corrected on the models on sale in stores.


In contrast to its Radeon HD 7950 DirectCU II, Asus has developed a totally customised and improved PCB here for the Radeon HD 7970 DirectCU II. The power stage benefits of course and there are now 10 phases for the GPU. Two 8-pin connectors are required for the power stage.


Moreover, Asus has included the VGA HotWire system which allows advanced users to connect the Radeon HD 7970 DirectCU II to an ROG motherboard so that the GPU, memory and PLL voltage can be read directly.


The bundle

The bundle includes a small manual, a CD with the drivers, a DVI to HDMI adaptor, a CrossFireX bridge, a 2x6 pin to 8-pin power supply converter and a small radiator to be placed on the power stage when using an alternative cooling system.

In terms of software, Asus supplies GPU Tweak, based on Rivatuner and GPU-Z. This allows you to modify clocks and voltages (on Asus cards only), offers a monitoring system and a bios update.

The card is guaranteed for two years.


Overclocking, undervolting and energy consumption
Here are the various configurations we obtained with the Radeon HD 7970 DirectCU II (GPU clock / memory clock @ GPU voltage):

1000 / 1400 MHz @ 1.050V: 163W
1000 / 1400 MHz @ 1.174V: 208W (by default)
1150 / 1775 MHz @ 1.174V: 237W
1175 / 1775 MHz @ 1.200V
1200 / 1775 MHz @ 1.225V

Note that the last two clocks were stable on the bench table but not in our closed casing. The energy consumption, temperature and noise readings were therefore taken at 1150 MHz.

When we increased the GPU voltage, the fans seemed to accelerate too slowly to keep pace with GPU leakage which increase as the temperature goes up - by the time the fans have accelerated a notch, energy consumption has already increased taking heat levels up and so on. The cooling system accelerates constantly up to 100% though never catching the GPU, whose temperature continues to climb until it reaches 100 įC and crashes. If however the fan speed is fixed manually, for example at 90%, the GPU temperature remains under control and overclocking is perfectly stable.


Infrared thermography

[ At idle ]  [ In load ]  [ Overclocking ]


[ At idle ]  [ In load ]

The Radeon HD 7970 DirectCU II is very well cooled, both at idle and in load or overclockedÖ at least when the GPU voltage isnít altered.


Temperature and noise readings

The GPU is better cooled than the reference card, in spite of the factory overclocking and noise levels are a good deal lower in load. The DirectCU II cooling system is also quieter than the reference cooling system at idle.

The RPMs as a % of the fan speed are as follows:

10%: 1080 RPM
41%: 2130 RPM
47%: 2350 RPM
100%: 3265 RPM


Our opinion
The factory overclocked Asus Radeon HD 7970 DirectCU, whether a TOP version or not, does better than the reference card in terms of cooling and is much quieter in load. As usual with the DirectCU II models, the finish is excellent, though this is a very big card and is quite expensive.

With this entirely customised model, Asus has taken the opportunity to revisit the connectivity and offer up to six video outs without a DisplayPort hub, compared to four on derivatives of the reference model.

We would however have liked Asus to work a bit more on the calibration of the cooling system so as to deal with extreme overclocking better. If they didn't because of the impact this has on noise levels during standard use of the card, they could always have provided an alternative bios for overclocking enthusiasts.


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Page 7
Review: HIS Radeon HD 7950

HIS HD 7950
With its first model, HIS has given us what is in effect the Ďrealí reference Radeon HD 7950, which includes the PCB developed by AMD to reduce production costs and an axial cooling system, also developed by AMD. HIS supplied us with a model in keeping with the reference clocks:

HIS Radeon HD 7950 3 GB


The card




The reference Radeon HD 7950 is slightly more compact than the press model derived from the Radeon HD 7970 and has a 26 cm PCB beyond which the cooling system casing extends by a few mm.

This cooling system has been simplified as far as possible and consists of a very small cooling block made up of a vapour chamber incrusted into an aluminium radiator cooled by an 8 cm fan. Thereís a plastic casing covering all this and a second casing covers the entire card to give it solidity, channel the flow of air a bit and give it a nicer look. Thereís no specific cooling for the memory modules or the sensitive power stage components.

The reference connectivity is reproduced on this PCB: a DVI out, an HDMI out and two DisplayPort outs. It has 12 GDDR5 Hynix T2C memory modules certified at 1.25 GHz. HIS has retained the dual bios switch, which gives access to the backup bios.


This power stage, which is based on less expensive components than those used for the reference Radeon HD 7970, provides 6 phases for the GPU as well as two for the memory. Two 6-pin power supply connectors are required, which is in keeping with the TDP announced at 200W for this graphics card.


The bundle

HIS supplies a small manual, a CD with drivers, a DVI to HDMI adaptor (not included with our model), a DVI to VGA adaptor, a CrossFire X bridge and a Weight Lifter add on for a long graphics card. This is designed to prevent the weight being a problem, mainly during transportation, when the card is positioned horizontally as it is in most casings.

The card is guaranteed for two years.


Overclocking, undervolting and energy consumption
Here are the various configurations we were able to get with the HIS Radeon HD 7950 (GPU clock / memory clock @ GPU voltage):

800 / 1250 MHz @ 0.925V: 104W
800 / 1250 MHz @ 1.093V: 133W (by default)
1000 / 1500 MHz @ 1.093V: 158W
1050 / 1500 MHz @ 1.150V
1075 / 1500 MHz @ 1.174V
1100 / 1500 MHz @ 1.200V
1125 / 1500 MHz @ 1.250V: 220W

Once the voltage was reduced, our test sample got very close to 100W! However, extreme overclocking causes the energy consumption to increase by 65%.


Infrared thermography

[ At idle ]  [ In load ]  [ Overclocking ]


[ At idle ]  [ In load ]

The HIS Radeon HD 7950 is well cooled overall, both at idle and in load, though its power stage would have benefitted from a small dedicated radiator. This only poses a problem however with major overclocking where the GPU voltage is also increased. Temperatures then increase to such an extent that they put the cardís long term survival in question.


Temperature and noise readings

This cooling system is slightly less efficient than the one on the card distributed by AMD to the press but thereís not a huge difference. Noise levels are slightly higher but the GPU doesnít heat up quite as much. It is however quieter at idle.

The RPMs as a % of the fan speed are as follows:

30%: 1270 RPM
58%: 3210 RPM
78%: 4275 RPM
100%: 4740 RPM


Our opinion
The HIS Radeon HD 7950, like the reference one, seems to have been designed with space for more aggressive pricing to kick in once the competition delivers new cards to market. The design is however quite effective for a Ďbudgetí model but not adapted to major overclocking.


Page 8
Review: MSI Radeon HD 7950 Twin Frozr III

MSI R7950 Twin Frozr III
MSI has combined the reference PCB with an in-house cooling system for its Twin Frozr version of the Radeon HD 7950, also offering a slight GPU overclocking, uping it from 800 to 880 MHz. MSI supplied us with a sample for testing:

MSI R7950 Twin Frozr 3GD5/OC


The card




Although the reference PCB produced here by MSI is just 26 cm long, the casing sticks out over the back of the card by a few mms.

MSI has gone for version III of its Twin Frozr cooling system here. It consists of an aluminium base from which lead five nickel plated copper pipes (no direct contact), two of which are 8 mm wide and three the more standard 6 mm diameter. They link up with a big aluminium radiator that extends across almost the entire length of the card and is cooled by two 80 mm fans. An aluminium casing covers the cooler and refines the overall look.

A metallic plate ensures the solidity of the card and is in contact with the memory modules as well as with the sensitive power stage components.

The reference connectivity is reproduced on this PCB: a DVI out, an HDMI out and two DisplayPort outs. It has 12 GDDR5 Hynix T2C memory modules certified at 1.25 GHz. MSI has retained the dual bios switch, which gives access to the backup bios.


This power stage, which is based on less expensive components than those used for the reference Radeon HD 7970, provides for 6 phases for the GPU as well as two for the memory. Two 6-pin power supply connectors are required, which is in keeping with the TDP announced at 200W for this graphics card.


The bundle

MSI supplies two small manuals, a CD with drivers (not included on our model), a DVI to VGA adaptor, a mini-DP to DisplayPort, a CrossFire X bridge and two double molex to 6-pin PCI Express power supply cable convertors.

In terms of software, MSI supplies Afterburner, based on Rivatuner and GPU-Z. This allows you to modify clocks and voltages and offers a monitoring system and a bios update tool.

The card is guaranteed for two years.


Overclocking, undervolting and energy consumption
Here are the various configurations we were able to get with the MSI Radeon HD 7950 Twin Frozr (GPU clock / memory clock @ GPU voltage):

800 / 1250 MHz @ 0.925V: 118W
880 / 1250 MHz @ 1.093V: 141W (by default)
1025 / 1775 MHz @ 1.093V: 167W
1100 / 1775 MHz @ 1.150V
1125 / 1775 MHz @ 1.174V
1150 / 1775 MHz @ 1.200V
1175 / 1775 MHz @ 1.250V
1200 / 1775 MHz @ 1.275V: 251W

The 880 MHz factory overclocking reduces somewhat the undervolting ability but our test sample still had plenty of additional room for overclocking.


Infrared thermography

[ At idle ]  [ In load ]  [ Overclocking ]


[ At idle ]  [ In load ]

The Radeon HD 7950 Twin Frozr is very well cooled, both at idle and in load, even when overclocked.


Temperature and noise readings

Although the card does a good deal better than the reference model in terms of noise levels, the low GPU temperature leads us to think that MSI could have better optimized the calibration of its cooling system.

The RPMs as a % of the fan speed are as follows:

31%: 1375 RPM
53%: 2860 RPM
77%: 4350 RPM
100%: 4710 RPM


Our opinion
With the Twin Frozr III, MSI has given us a pretty effective, well made Radeon HD 7950. We don't have much against it except that in load the cooling system seems to be calibrated to favour heat reduction too much over noise, in contrast to the Sapphire OverClock model that strikes a better compromise.

Please note that at some point during the commercial life of this Radeon HD 7950 Twin Frozr III, MSI as upgraded its PCB with the reference HD 7970 one. A beneficial evolution.


Page 9
Review: MSI Radeon HD 7970 Lightning

MSI R7970 Lightning
With the Radeon HD 7970 Lightning, MSI has produced a high-end, fully customised Radeon HD 7970, all their own work from cooler to PCB. It also enjoys a factory overclocking that takes the GPU from 925 to 1070 MHz (+16%) and the memory, more modestly, from 1.375 GHz to 1.4 GHz (+2%). MSI supplied us with a sample for testing:

MSI R7970 Lightning


The card






Like any extreme model of a high-end graphics card, the MSI R7970 Lightning is pretty big. Its PCB is therefore 1 cm longer than the one on the reference card and its cooler sticks out a further 1.5 cm, taking it to a total length of 30 cm. Whatís more the PCB is 1.8 cm higher and again the cooling system extends beyond this increasing the height of the card by an additional 2.5 cm.

MSI hasnít forgotten the third dimension either, with a protuberance at the back of the card that encloses a small additional circuit. At a thickness of 9 mm, it will, in many cases, prevent the use of the slot situated directly behind the slot used by the Lightning, which could pose a problem with some multi-card configurations.

The cooling system MSI has gone for is the Twin Frozr IV, a slight development of the Twin Frozr III. It is similarly constructed with, here, a nickel-plated copper base from which lead five nickel-plated copper pipes (no direct contact), two of which are 8 mm wide and three the more standard 6 mm diameter. They link up to an aluminium radiator which is however much bigger and cooled by two 92 mm fans. On start-up, they run backwards for a few seconds to reduce the accumulation of dust. More attention has been given to the aluminium casing to give the card a less raw aesthetic, but as it is thinner the card is less rigid.

As the cooling system is only fixed around the GPU with four screws, a metallic plate is used to ensure the rigidity of this big PCB and is in contact with the Hynix ROC memory modules (certified at 1.5 GHz) as well as with the sensitive power stage components. Finally, thereís a perforated metal plate at the back of the card but it isnít in contact with the PCB or other components. It doesnít therefore serve any cooling purpose but is there rather for aesthetic reasons as well as to protect the back of the PCB.

Overall, itís pretty well finished but adding a few small pads on the extremeties of the casing and between the metallic plate and the radiator would have improved it, giving it more robustness. Note that some small blue diodes illuminate the two fans as well as the power stage and the part sticking out at the back of the GPU.

MSI has revisited the reference connectivity to give us two DVI outs and four DisplayPort outs. Like our Asus 7970 DirectCU II, our test model of the Lightning wouldnít display anything on our 30" monitor: black screen with the driver loaded on both DVI outs. We therefore used an active dual-link adaptor from DisplayPort.


On this Radeon HD 7970, MSI has totally revisited the power stage and there are now no less than 14 phases for the GPU, which moreover have been built with high-end components optimised to resist overheating. This power stage is designed to deliver 500W to the GPU (425A) whereas the reference design only aims to supply 250W (210A). The power stage requires two 8-pin PCI Express connectors.

MSI uses the second bios to give us a version optimised for huge overclocking, mainly via LN2, however it disables the factory overclocking and OCP (Over Current Protection) taking the GPU overconsumption protection from 260A to 460A. It also disables and Active Phase Switching (APS) which limits the number of phases according to load, so as to reduce energy consumption. These phase changes can reduce the stability of voltages during extreme overclocking.



MSI has also added a small additional circuit, known as the GPU Reactor, to the back of the GPU so as to be able to offer as clean a power supply signal as possible. The GPU Reactor contains several additional capacitors charged with smoothing out the signal. We were able to see the advantage of the Reactor in practice as, during overclocking, not using this module meant we had to increase the GPU voltage by 0.025V to get the same results as with it. Apart from the fact that this gives the card an original design, which you have to think may well be the point of it, it would have made more sense to integrate this circuit as part of the main PCB.

Finally, as usual, MSI has set up contact points to give GPU, memory and PLL voltage readings.


The bundle

MSI delivers its card with a small manual, a quality certificate, a CD for the drivers, a DVI to HDMI adaptor, a mini-DP to DisplayPort, a CrossFire X bridge, two 6-pin to 8-pin power supply converters and some small wires to place on the voltage read points to facilitate usage.

In terms of software, MSI supplies Afterburner, based on Rivatuner and GPU-Z. This allows you to modify clocks and voltages (GPU, memory and PLL on the Lightning) and offers a full monitoring system.

The card is guaranteed for two years.


Overclocking, undervolting and energy consommation
Here are the various configurations that we were able to obtain with the Radeon HD 7970 Lightning (GPU clock / memory clock @ GPU voltage):

1070 / 1400 MHz @ 1.150V: 202W
1070 / 1400 MHz @ 1.174V: 211W (by default)
1100 / 1775 MHz @ 1.174V: 225W
1125 / 1775 MHz @ 1.200V
1150 / 1775 MHz @ 1.225V: 256W

As always overclocking is a lottery and our test model wasn't particularly cooperative and certainly didnít push the Lightningís power stage to the limit.

With the second bios, the card runs by default in load at 925 / 1375 MHz @ 1.174V and then consumes 200W. At idle, energy consumption is however up from 25W to 36W because of the deactivation of APS. This doesnít however have an impact in prolongued standby as the GPU power stage is then turned off in both cases.


Infrared thermography

[ At idle ]  [ In load ]  [ Overclocking ]
[ At idle bios 2 ]  [ In load bios 2 ]



[ At idle ]  [ In load ]

The Radeon HD 7970 Lightning is very well cooled, at idle and in load or overclocked.


Temperature and noise readings

While the GPU is very well cooled in load, noise levels are rather high due to the significant factory overclocking and higher than those for the reference card. For information, when the R7970 Lightning is clocked at the reference clocks, with the second bios we measured it at 47.3 dBA with the fans then running at 2570 RPM.

The RPMs as a % of the fan speed are as follows:

31%: 1090 RPM
69%: 2570 RPM
74%: 2770 RPM
100%: 3090 RPM


Our opinion
With the R7970 Lightning, MSI wanted to offer a Radeon HD 7970 that could handle extreme load situations. The final result isnít however entirely convincing: while the PCB does indeed have the sturdiest power stage currently available, the cooling system, though not bad, isnít at the same level. Thus only extreme overclocking enthusiasts will fully make use of the power stage, replacing the cooler with an LN2 type system and betting on lucking out with a particularly cooperative GPU to reach record scores.

Paradoxically, more common users with no interest for manual overclocking are probably the ones who will benefit most from this extreme model, which already draws heavily on the available overclocking margin. Without getting in there and messing around you already enjoy a relatively high factory overclocking combined with moderate GPU and power stage temperatures, which makes this model a good bet in terms of reliability. Noise levels will however be rather high, a little higher than on the reference card in load, though the Lighting is quieter at idle.

You will require a configuration with plenty of space as the card is longer and higher than others and blocks the slot just behind it. It does however come with richer connectivity giving up to six video outs compared to just four on reference model derivatives.


Page 10
Review: PowerColor Radeon HD 7950 PCS+

PowerColor HD 7950 PCS+
PowerColor has brought together the reference PCB with a much higher performance in-house cooling system for its PCS+ version of the Radeon HD 7950, also offering a slight GPU overclocking, uping it from 800 to 880 MHz. PowerColor supplied us with a sample for testing:

PowerColor Radeon HD 7950 PCS+ 3 GB


The card



While the reference PCB produced here by PowerColor is just 26 cm long, the casing sticks out over the back of the card several mm. The relatively large cooling system is moreover 2 cm higher than the PCB.

The PCS+ cooling system has a copper base from which lead three large 8 mm heat pipes (no direct contact) in nickel-plated copper. They link up to a big aluminium radiator cooled by two low profile 92 mm fans. A soft touch plastic casing covers the cooling system and gives a high-end finish to the card.

A metal support bar is fixed above the PCB so as to ensure the rigidity of the system, which is important given that the cooling system is only fixed on via the four holes placed in the four corners of the GPU. Thereís no specific cooling system for the memory modules or for the sensitive power stage components. They are however placed in the flow of air as the radiator isn't closed at its base.

This PCB has the same connectivity as on the reference model, namely a DVI out, an HDMI out and two DisplayPort outs. It has 12 GDDR5 Hynix T2C memory modules certified at 1.25 GHz. PowerColor has retained the dual bios switch, which gives access to the backup bios.


This power stage, which is based on less expensive components than those used for the reference Radeon HD 7970, provides for 6 phases for the GPU as well as two for the memory. Two 6-pin power supply connectors are required, which is in keeping with the TDP announced at 200W for this graphics card.


The bundle

PowerColor supplies a small manual, a CD with drivers (not included on our model), a DVI to HDMI adaptor, a mini-DP to DisplayPort adaptor and a DVI to VGA adaptor.

The card is guaranteed for two years.


Overclocking, undervolting and energy consumption
Here are the various configurations we managed to obtain with the PowerColor Radeon HD 7950 PCS+ (GPU clock / memory clock @ GPU voltage):

880 / 1250 MHz @ 0.975V: 127W
880 / 1250 MHz @ 1.031V: 141W (by default)
950 / 1650 MHz @ 1.031V: 157W
1025 / 1650 MHz @ 1.093V
1050 / 1650 MHz @ 1.150V: 215W

The factory overclocking of 880 MHz reduces the available margin in terms of undervolting. The GPU on our test card didnít manage anything beyond 1050 MHz, whatever the voltage applied.


Infrared thermography

[ At idle ]  [ In load ]  [ Overclocking ]


[ At idle ]  [ In load ]

The Radeon HD 7950 PCS+ is well cooled, both at idle and in load, even when overclocked.


Temperature and noise readings

While the card is well cooled, it manages to remain within reasonable noise limits: the Radeon HD 7950 PCS+ is quieter in load than some cards are at idle! Even when overclocked, noise levels are acceptable.

The RPMs as a % of the fan speed are as follows:

20%: 1320 RPM
38%: 1550 RPM
48%: 2080 RPM
100%: 3370 RPM


Our opinion
The PowerColor Radeon HD 7950 PCS+ will impress those looking for a quiet card - itís surprisingly quiet for a high-end graphics card. The apparently simple, though carefully designed, cooling system is very efficient and fully justifies the extra Ä30 youíll pay in comparison to basic models based on the reference cooling system.

We should however point out that PowerColor could have put in a small radiator to help with the cooling of sensitive power stage components during major overclocking.


Page 11
Review: Sapphire Radeon HD 7950

Sapphire HD 7950
The Sapphire Radeon HD 7950 is based on the reference design but equipped with a different casing to customise the overall look a bit. We got hold of a sample from a store:

Sapphire Radeon HD 7950 3 GB


The card




The reference Radeon HD 7950 is slightly more compact than the press model derived from the Radeon HD 7970 and the PCB is just 26 cm long. The Sapphire casing extends a centimetre beyond it. The design of the casing is questionable, especially as the plastic used and the little chrome touch give a rather cheap look to the card.

The cooling system has been simplified as far as possible and in fact now consists of a small block made up of a vapour chamber set into an aluminium radiator that is cooled by an 8 cm fan. Thereís a plastic casing covering all this and a second casing covers the entire card to give it solidity, channel the flow of air a bit and give it a nicer look. Thereís no specific cooling for the memory modules or the sensitive power stage components.

The reference connectivity is reproduced on this PCB: a DVI out, an HDMI out and two DisplayPort outs. It has 12 GDDR5 Hynix T2C memory modules certified at 1.25 GHz. Sapphire has retained the dual bios switch, which gives access to the backup bios.


This power stage, which is based on less expensive components than those used for the reference Radeon HD 7970, provides for 6 phases for the GPU as well as two for the memory. Two 6-pin power supply connectors are required, which is in keeping with the TDP announced at 200W for this graphics card.


The bundle

The Sapphire card comes with plenty in the bundle: a small manual, a quality certificate, a CD for the drivers, a DVI to HDMI adaptor, a mini-DP to DisplayPort, a DVI to VGA adaptor, a 1.8 m HDMI cable, a CrossFire X bridge and two 6-pin power supply converters.

In terms of software, Sapphire supplies TriXX, which allows you to overclock the graphics card, modify GPU voltage and control the fan/fans.

The card is guaranteed for two years.


Overclocking, undervolting and energy consumption
Here are the various configurations that we were able to obtain with the Sapphire Radeon HD 7950 (GPU clock / memory clock @ GPU voltage):

810 / 1250 MHz @ 0.950V: 115W
810 / 1250 MHz @ 1.031V: 133W (by default)
950 / 1450 MHz @ 1.031V: 150W
1025 / 1450 MHz @ 1.093V
1075 / 1450 MHz @ 1.150V
1100 / 1450 MHz @ 1.174V
1125 / 1450 MHz @ 1.200V: 233W
1150 / 1450 MHz @ 1.225V

Note that a GPU clock of 1150 MHz was stable on the bench table but not in the closed casing, which our observations show comes from an overheated power stage. We therefore took the energy consumption, noise and temperature readings at 1125 MHz.


Intrared thermography

[ At idle ]  [ In load ]  [ Overclocking ]


[ At idle ]  [ In load ]

While the card is sufficiently well-cooled at idle and in load, major overclocking does cause problems for the power stage, which then heats up dangerously.


Temperature and noise readings

The Sapphire Radeon HD 7950 is quiet at idle and less noisy in load than the modle supplied by AMD to the press. It is also less noisy than the HIS Radeon HD 7950, though they both have the same design except for the exterior casing. This is probably due to several factors: the casing, the fan calibration and a variation between several samples of this fan.

Note that when the card is overclocked it reaches its cooling capacity limit.

The RPMs as a % of the fan speed are as follows:

26%: 1180 RPM
54%: 2960 RPM
100%: 4590 RPM


Our opinion
The reference Radeon HD 7950, as sold by Sapphire, would seem to have been designed to give the company the option of pricing it more agressively as competitor cards appear on the market. Its design does however seem quite efficient for a Ďbudgetí version, though you shouldnĎt use it for major GPU overclocking. The bundle is also very generous and includes an HDMI cable.


Page 12
Review: Sapphire Radeon HD 7950

Sapphire HD 7950 OverClock
Sapphire is also offering a second Radeon HD 7950, based on the same reference PCB but equipped with a sturdier cooling system. An Overclock, or OC, it has a GPU clock of 900 MHz, which is a 12.5% overclocking. Sapphire supplied us with a sample for testing:

Sapphire Radeon HD 7950 Overclock 3 GB


The card




The reference Radeon HD 7950 is slightly more compact than the press model derived from the Radeon HD 7970 and the PCB is just 26 cm long. The Sapphire casing extends a little more than two centimetres beyond it at the back (without any reason) and 1.5 cm on top (mainly to accommodate the bigger cooling system). The design of the casing is questionable, especially as the plastic used and the little chrome touch give a rather cheap look to the card.

Under this casing there is however a pretty sturdy cooling system with a massive copper base from which lead five heatpipes, three of which are 6 mm in diameter and two 8 mm, which join up to a wide aluminium radiator. Two low profile 92 mm fans create a flow of air across this radiator.

A metal plate is in contact with memory modules and the sensitive power stage components and provides solidity for the card structure.

The reference connectivity is used for this PCB, giving us a DVI out, an HDMI out and two DisplayPort outs. It has 12 GDDR5 Hynix T2C memory modules certified at 1.25 GHz. Sapphire has retained the dual bios switch, which gives access to the backup bios.


The power stage, which is based on less expensive components than those used for the reference Radeon HD 7970, provides for 6 phases for the GPU as well as two for the memory. Two 6-pin power supply connectors are required, which is in keeping with the TDP announced at 200W for this graphics card.


The bundle

This Sapphire card comes with plenty in the bundle: a small manual, a CD for the drivers, a Sapphire Select Club coupon, a DVI to HDMI adaptor, a mini-DP to DisplayPort adaptor, a DVI to VGA adaptor, a 1.8 m HDMI cable, a CrossFire X bridge and two 6-pin power supply converters.

In terms of software, Sapphire supplies TriXX, which allows you to overclock the graphics card, modify GPU voltage and control the fan/fans.

The card is guaranteed for two years.


Overclocking, undervolting and energy consumption
Here are the various configurations that we were able to obtain with the Sapphire Radeon HD 7950 OC (GPU clock / memory clock @ GPU voltage):

900 / 1,375 MHz @ 0.950V: 124W
900 / 1375 MHz @ 1.093V: 152W (by default)
1025 / 1725 MHz @ 1.093V: 177W
1075 / 1725 MHz @ 1.150V
1125 / 1725 MHz @ 1.174V
1150 / 1725 MHz @ 1.200V
1175 / 1725 MHz @ 1.225V: 246W


Infrared thermography

[ At idle ]  [ In load ]  [ Overclocking ]


[ At idle ]  [ In load ]

In spite of the factory overclocking, the Sapphire Radeon HD 7950 OverClock is very well cooled in load and when overclocked, including the power stage which benefits from contact with a metallic plate.


Temperature and noise readings

This card isnít only well-cooled, itís well cooled in silence, or at least at a very reduced level of noise in comparison to most other cards. The noise levels only increase when the GPU is clocked very high.

Note that these fans make more noise at 3040 RPM than 3500 RPM (linked to turbulence; if you stop one of them, this extra noise stops).

The RPMs as a % of the fan speed are as follows:

21%: 1175 RPM
49%: 2100 RPM
73%: 3040 RPM
100%: 3500 RPM


Our opinion
With the Radeon HD 7950 OverClock, Sapphire has done some very good work on the cooling system which is very good at keeping noise and heat down. True, the look of the card could be improved and the PowerColor PCS+ model is even quieter but by including direct cooling for the power stage, the Sapphire card is better adapted to extreme overclocking situations. The bundle is also very generous and includes an HDMI cable.


Page 13
Review: XFX Radeon HD 7950 Double Dissipation

XFX HD 7950 Double Dissipation
In addition to having a cooling system derived from the reference model, XFX is offering Radeon HD 7950 Double Dissipations at base clocks or in a Black Edition version with the GPU overclocked to 900 MHz and the memory to 1375 MHz, making for respective overclockings of 12.5 and 10%. XFX supplied us with a Radeon HD 7950 Black Edition Double Dissipation:

XFX Radeon HD 7950 Double Dissipation 3 GB
XFX Radeon HD 7950 Black Edition Double Dissipation 3 GB


The card



The reference Radeon HD 7950 PCB, in the XFX version here, is slightly more compact than the press model derived from the Radeon HD 7970 and is just 26 cm long. The aluminium casing is however identical to the one used on the Radeon HD 7970 and sticks out almost a centimetre over the back of the card. As on the HD 7970, the overall finish here is irreproachable, both in terms of solidity and how it looks.

While the cooling system looks the same as the one used on the XFX Radeon HD 7970 Double Edition, in reality it isnít. The big vapour chamber has been removed and been replaced by a much smaller one. For the rest, the system is similar: a big radiator cooled by two 90 mm fans. A metallic plate is used to ensure the rigidity of this big PCB and is in contact with the memory modules.

XFX explains that this Double Dissipaton design provides better cooling of the PCB components as the air can cross the radiator unlike systems with enclosed components. However, as you can see on the photo of the cooling system, the fins have been bent and condensed at the base of the radiator. The air cannot therefore cross it and the power stage is insulated from any air flow.

Finally, XFX has replaced the extraction grill by its in-house variant which has bigger openings. This isnít very important as far as this model goes as it hasn't been designed to expel hot air from the casing.

The reference connectivity is used for this PCB, giving us a DVI out, an HDMI out and two DisplayPort outs. It has 12 GDDR5 Hynix T2C memory modules certified at 1.25 GHz. XFX has however decided to do without the dual bios and switch. Nevertheless two different biosí are on offer to users, one optimised to reduce noise (by default) and the other to reduce temperatures (to be installed manually).


This power stage, which is based on less expensive components than those used for the reference Radeon HD 7970, provides for 6 phases for the GPU as well as two for the memory. Two 6-pin power supply connectors are required, which is in keeping with the TDP announced at 200W for this graphics card.


The bundle

The XFX card comes with a small installation guide to the card and drivers, a CD for drivers, an activation code for direct technical support, an HDMI to DVI adaptor, a CrossFireX bridge and a small badge.

The card is guaranteed for two years.


Overclocking, undervolting and energy consumption
Here are the various configurations that we were able to obtain with the Radeon HD 7950 Black Edition Double Dissipation (GPU clock / memory clock @ GPU voltage):

900 / 1,375 MHz @ 0.950V: 134W
900 / 1375 MHz @ 1.031V: 158W (by default)
950 / 1850 MHz @ 1.031V: 176W
1050 / 1850 MHz @ 1.093V
1125 / 1850 MHz @ 1.150V: 258W

With an original voltage of 1.031V for the GPU and factory overclocking of 900 MHz, there isnít much of an additional overclocking margin unless you increase the voltage. As on the XFX Radeon HD 7970 Double Dissipation, we managed to clock the memory very high on this model: +35% on the original clock and +48% above the clock at which the memory is certified. As the memory voltage isnít modified on the test card, we imagine that XFX made a pre-selection for us.


Infrared thermography

BIOS optimised for noise: [ At idle ]  [ In load ]  [ Overclocking ]
BIOS optimized for performance: [ At idle ]  [ In load ]  [ Overclocking ]



[ At idle ]  [ In load ]

In spite of the factory overclocking, the card is very well cooled in load, its power stage benefitting from direct contact with the base of the structure of the cooling system. The second bios, optimised for performance (temperatures), doesnít make a significant differenceÖ at least without overclocking. With overclocking the second bios allows you to reduce the temperature of the GPU and power stage.


Temperature and noise readings

You can see why XFX offers the option of a second bios when the card is overclocked. The original bios seems to accelerate more slowly, which means temperatures do go up during major overclocking while the second bios controls the heat better by accelerating a bit faster, though both end up at maximum speed.

Apart from this, the XFX Double Dissipation is noisier at idle than all the other Radeon HD 7950s tested and isn't particularly efficient in load.

The RPMs as a % of the fan speed are as follows:

20%: 1470 RPM
54%: 2490 RPM
55%: 2515 RPM
100%: 3520 RPM


Our opinion
The Double Dissipation systemís cooling capacity has been revised downwards in comparison to the cooler designed for the Radeon HD 7970, so that XFX hasnít taken full advantage of the reduced energy consumption of the Radeon HD 7950 to cut noise levels. While this model does a bit better than the reference design versions of the Radeon HD 7950, there isnít enough of a difference to justify the pricing premium, especially as the PowerColor PCS+ and Sapphire OverClock do a good deal better.


Page 14
Review: XFX Radeon HD 7970 Double Dissipation

XFX HD 7970 Double Dissipation
In addition to the reference Radeon HD 7970 models, XFX is also offering Double Dissipation versions, both standard and overclocked (Black Edition) to 1 GHz for the GPU, making for a gain of 8% over the base clock. XFX supplied us with a standard Radeon HD 7970 Double Dissipation:

XFX Radeon HD 7970 Double Dissipation 3 GB
XFX Radeon HD 7970 Black Edition Double Dissipation 3 GB


The card


The PCB used on the XFX Radeon HD 7970 Double Dissipation Edition is identical to that used on the reference card.

The cooling system has however been fully revisited. The blower fan has been replaced with two axial fans which cool a big radiator fixed to a big vapour chamber, similar to the one used by AMD on the reference design. A metallic plate is used to ensure the rigidity of the PCB and is in contact with the sensitive power stage components as well as the memory modules.

XFX explains that this Double Dissipaton design provides better cooling of the PCB components as the air can cross the radiator in opposition to systems, like the reference one, which enclose the components. As you can see on the photo of the cooling system, the fins have been bent and condensed at the base of the radiator. In practice, the air cannot therefore cross it and the power stage is therefore insulated from any air flow.

Finally, XFX has replaced the extraction grill by its in-house variant which has bigger openings. This isnít very important as far as this model goes as it hasn't been designed to expel hot air from the casing.

The overall finish is irreproachable and the combination of brushed grey and red aluminium gives this card a very nice look.

The reference connectivity is used for this PCB, giving us a DVI out, an HDMI out and two DisplayPort outs. It has 12 GDDR5 Hynix ROC memory modules certified at 1.5 GHz. XFX has retained the dual bios switch, which gives access to the backup bios.


This PCB has been designed with 6 phases for the GPU, with high quality components. The Radeon HD 7970 however uses just 5 of these phases with 8+6-pin connectors, for a TDP of 250W.


The bundle
XFX supplies a small installation guide to the card and drivers, a CD for drivers, an activation code for direct technical support, an HDMI to DVI adaptor, a CrossFireX bridge and a small badge.

The card is guaranteed for two years.


Overclocking, undervolting and energy consumption
Here are the various configurations that we were able to obtain with the Radeon HD 7970 Double Dissipation (GPU clock / memory clock @ GPU voltage):

925 / 1375 MHz @ 1.025V
925 / 1375 MHz @ 1.174V: 203W (by default)
1100 / 1900 MHz @ 1.174V: 244W

Unfortunately, we no longer had the card when we decided to take readings at different GPU voltages, which is why these readings arenít included here.


Infrared thermography

[ At idle ]  [ In load ]  [ Overclocking ]


[ At idle ]  [ In load ]

In load, the power stage on the XFX Radeon HD 7970 DDE heats up more than the reference card, though temperatures donít get up too high to threaten the life of the card. In spite of what XFX says, this confirms our initial impression that the cooling system here isolates the power stage more than is the case on the reference card.

Temperature and noise readings

At idle, the XFX Radeon HD 7970 DDE is noisier than the reference Radeon HD 7970 but things are the other way round in load, with levels even more to XFXís advantage when the cards are overclocked.

The XFX Radeon HD 7970 DDE seems to have a similar calibration system to the one used on the reference card, which maintains GPU temperatures at 41 įC at idle. In load however, the GPU temperature on the XFX model is higher as XFX has prioritised noise levels here.

The RPMs as a % of the fan speed are as follows:

20%: 1460 RPM
55%: 2575 RPM
61%: 2880 RPM
100%: 3630 RPM


Our opinion
While this card has an excellent finish, the Double Dissipation system isnít really any more efficient than the reference system. Itís a little less so at idle and similar in load. It is however better calibrated as far as weíre concerned: by default, it is quieter but allows the GPU temperature to get a bit higher.

It should however be noted that as it only expels a little of the hot air generated by the graphics card out of the casing, the results you get with it will depend on how well your casing is cooled. Our casing is reasonably (though not very) well ventilated for a high-end system. If yours is poorly ventilated, the card wonít do as well for you, but if you have a very well ventilated casing, it could do better than it did in our tests.


Page 15
Summary of results

Summary of results
We have brought together all the temperature readings taken:



At idle, all the cards do well and the GPUs are well cooled.




In load, we noted a few differences, the most significant of which is linked to the fact that only the reference Radeon HD 7970 and the 7950 press edition send most of the hot air out of the casing. This mainly benefits the CPU, as the hard drives benefit from the cool flow of air in the new test casing and therefore arenít as affected by the hot air coming from the graphics cards. The reference HIS, MSI Twin Frozr III and Sapphire OverClock Radeon HD 7950s and Radeon HD 7970 Lightning however tend to direct more hot air towards the hard drives.


Page 16
Temperature and noise levels

GPU temperatures
We have shown the various GPU temperatures at idle and in load:


The differences in GPU temperature arenít great. The XFX Double Dissipation models do however allow the GPUs to get hotter at load than the other cards.


Noise levels
Here weíve displayed the readings for cards alone:


This is where the cards differentiate themselves most from each other. The XFX models are the noisiest at idle while the Radeon HD 7950s based on the low cost reference cooling system are the quietest.

In load, the differences are more marked: The PowerColor Radeon HD 7950 PCS+ is by far the quietest. The Sapphire Radeon HD 7950 Overclock also does pretty well.

Comparing the Radeon HD 7970s, the Asus DirectCU II TOP does best, in spite of the factory overclocking. The MSI Radeon HD 7970 Lightning doesnít do any better than the reference card.


Page 17
Infrared thermography: graphics cards

Infrared thermography: graphics cards

HD 7950 press edition
Reference HD 7970
Asus HD 7970 DirectCU II TOP
HIS HD 7950
MSI R7950 Twin Frozr III
MSI R7970 Lightning
PowerColor HD 7950 PCS+
Sapphire HD 7950
Sapphire HD 7950 OverClock
XFX HD 7950 Black Edition Double Dissipation
XFX HD 7970 Double Dissipation
  [ Idle ]  [ Load ]
  [ Idle ]  [ Load ]
  [ Idle ]  [ Load ]
  [ Idle ]  [ Load ]
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At idle, all the Radeon HD 7900s are well cooled, but the power stage on some Radeon 7950s does heat up slightly.

In load, among the Radeon HD 7970s, the power stage on the XFX Double Dissipation heats up the most while the very sturdy MSI Lightning heats relatively little.

Among the Radeon HD 7950s, the Sapphire OverClock is the best cooled. On the XFX Black Edition Double Dissipation the GPU heats up most and on the cards based on the reference cooling system (HIS and Sapphire) the power stage suffers most.


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Infrared thermography: systems

Infrared thermography: systems

HD 7950 press edition
Reference HD 7970
Asus HD 7970 DirectCU II TOP
HIS HD 7950
MSI R7950 Twin Frozr III
MSI R7970 Lightning
PowerColor HD 7950 PCS+
Sapphire HD 7950
Sapphire HD 7950 OverClock
XFX HD 7950 Black Edition Double Dissipation
XFX HD 7970 Double Dissipation
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None of the cards tested poses any particular problem in terms of the temperatures inside the casing. Nevertheless those Radeon HD 7970s that don't expel hot air from the casing do cause internal heat levels to rise and the HIS, MSI Twin Frozr III and Sapphire SuperClock Radeon HD 7950s and the Radeon 7970 Lightning tend to expel more hot air towards the hard drives than the other cards.


Page 19
Overclocking and undervolting

Overclocking
Not all GPUs are the same and not all cards with certain specifications have an identical profile. This is a result of manufacturing variability and certain GPUs therefore need higher voltages to maintain the desired clock, while others, with big current leakages, have to be run on relatively low voltages In order to remain within the thermal envelope.

In order to equalise things out, AMD hasnít attempted to reduce energy consumption beyond this thermal envelope. In other words if a Tahiti GPU is given as being clocked at 925 MHz within a TDP of 250W with a high voltage, AMD will not look to find out if the GPU could in reality be validated with a lower voltage and therefore consume less power. This sort of stringent selection process would only make any sense on a product such as the Radeon HD 7990 or a mobile version of the Radeon HD 7900s, which however are unlikely to appear.

There are several points to be raised here. On one hand, the overclocking potential will be significant on many cards, though exceeding the given TDP by a little or a lot depending on the sample, and on the other it will be possible to undervolt some cards, reducing their voltage to reduce power consumption.

Donít put any faith in the GPU quality rating from GPU-Z as it doesn't mean much here. As AMD obviously has no Ďqualityí parameter, this is simply a quick interpretation made of the value of a register by GPU-Z. In practice this value is more of a measure of the current leakage during validation but doesnít measure the quality of a GPU, which is moreover a subjective notion.

The voltage on a Tahiti GPU can vary on the Radeon HD 7970 as much as on the Radeon HD 7950. We have seen samples of Radeon HD 7970s at 1.174V and samples of Radeon HD 7950s at 1.031V and 1.093V.

Note that weíre talking about the voltages requested at the power stage, which, depending on its quality, manages to maintain them during high load to a greater or lesser extent. In practice they vary and are on average lower by between 0.030 and 0.080V, according to the GPU-Z monitoring.

Finally itís important to remember that PowerTune maintains the graphics card within a given thermal envelope. The technology doesnít however measure energy consumption directly, but estimates it using a table of watts corresponding to load levels for different blocks of the GPU. Note: the formula used takes the GPU clock into account but not the voltage!


This implies several things. Firstly, during significant overclocking you have to increase the PowerTune limit to prevent the technology reducing the clock - it often reduces the clock more than it has been clocked up and ends up actually reducing performance!

Secondly, PowerTune doesnít register increases in the GPU voltage and the big energy consumption increases that come with it. The technology is therefore incapable of fully protecting the GPU and the card. AMD says that OVP (Over Voltage Protection) and OCP (Over Current Protection) are still in place but, as we were able to observe, these technologies cut all power to the card when limits are exceeded. They are also set quite high and donít necessarily prevent long term damage to the card and, more particularly, to the power stage, which can be subjected to a higher level of stress and heat than those for which they have been designed. We therefore recommend you to be prudent when massively overclocking the GPU by increasing voltages supplied to it on cards which donít have an appropriate power stage cooling system.


Results
While of course any individual card may behave differently when it comes to overclocking, we did try to push all the cards we tested as far as possible so as to see if we could observe a few generalities. Note that the reference Radeon HD 7970, the Radeon HD 7950 press edition, the Asus Radeon HD 7970 DirectCU II, the HIS Radeon HD 7950, the Radeon HD 7950 Twin Frozr III, the Radeon HD 7970 Lightning, the PowerColor Radeon HD 7950 PCS+, the Sapphire Radeon HD 7950 OverClock and the XFX Radeon HD 7950 and 7970 Double Dissipations were supplied to us by their respective manufacturers, while the standard Sapphire Radeon HD 7950 was from a store.

On an open test system, we used Crysis Warhead and 3DMark 11 to load the cards up in such a way so as to ensure stablility. We then subjected the cards to a 45 minute stress test in 3D Mark 11 with the casing closed. We used MSI Afterburner to overclock the cards as it allows you to modify the GPU voltage on all the reference Radeon HD 7970s and 7950s. We increased the PowerTune limit to +20%, which was enough to stop the technology reducing the clocks during these tests.

Firstly we wanted to observe the minimum voltage at which each card was stable at its starting clocks:


Unsurprisingly, we observed the following trend: the higher the GPU clock, the higher the minimum voltage.

Without changing the GPU voltage, we then tried to obtain the maximum stable GPU clock, by moving up in 25 MHz steps. Once weíd reached this maximum clock, we did the same with the GDDR5 memory. Note that GDDR5 memory has different mechanisms for the detection of errors that mean that although the memory remains stable when overclocked significantly, it can take a lot of time to correct the associated errors, either by returning the corrupted data or recalibrating frequencies. We checked performances to make sure that this wasnít happening Ė where it was we took a step backwards. We did observe the phenomenon on the Radeon HD 7970 DirectCU II, all the other cards having crashed before memory performance was affected.

Here are the clocks we obtained for the memory:


Thereís a relatively high overclocking potential here as you can see. This is probably due to two factors: AMD has designed its memory controllers for very high clocks and GDDR5 production is now sufficiently mature for most of the memory produced to have a very high clock capacity, even though it's sold with lower specs.

We then gradually increased GPU voltage until we couldnít obtain any further clock increase. The first value given for each card represents the starting voltage while the orange boxes represent cases where cards were stable on the bench table but not in the casing, where temperatures get higher.


The maximum clock on the Radeon HD 7900s generally seems to be between 1125 and 1200 MHz when the GPU voltage is adjusted.

Without changing the GPU voltage, you can see that there's a correlation between the original voltage and the maximum clock that you can reach at this voltage.


Page 20
Energy consumption

Energy consumption
We measured the energy consumption of the different cards, keeping in mind that thereís often a variation between two sample of a given model, due, among other things, to leaks in current and GPU voltages. Moreover, some run at higher clocks as they are factory overclocked.

We measured the graphics card energy consumption at idle on the Windows desktop and in load in Anno 2700 at 1920x1080 with all graphics options pushed to a max.


At idle, the energy consumption of the Radeon HD 7900s varies between 15 and 19W, except for the MSI Radeon HD 7970 Lightning which draws more power. Note that with the screen in standby, they all draw 2W except the Lightning (4W) and turn their fans off.

In load, the Radeon HD 7970s understandably consume more energy than the Radeon HD 7950s with an additional +/- 50W registered.

We also wanted to group all the energy consumption readings in terms of undervolting and overclocking, not so we can judge a particular product (as the results vary from one sample to another) but to give you an overall idea of the difference you can expect:


Hold the mouse over the graph to display energy consumption in watts

Lowering the GPU voltage allows you to reduce the energy consumption of the card by between 4 and 29%, with a lot of variation from one model to another and the models with a significant factory overclocking having less undervolting capacity.

Without any alteration in GPU voltage, overclocking increases energy consumption by between 7 and 24% across all cards tested. When the GPU voltage is changed this goes up to an increase of between 21 and 78%, which is enough to put the power stages of these cards under stress.


Page 21
Performance

Performance
For information, we observed the performance of all the cards at their original clocks and when overclocked in Battlefield 3, at 1920x1080 Ultra:



Hold the mouse over the graph to display performance in comparison to the Radeon HD 7970

When overclocked but without any alteration to the GPU voltage, the Radeon HD 7950s generally perform at the same level as the Radeon HD 7970 at its base clocks. Changing the GPU voltage allows them to go a lot further in some cases and outperform the 7970 at base clocks by 20% and the Radeon HD 7950 at its reference clocks by 40%!


Page 22
Conclusion

Conclusion
This report on the first Radeon HD 7900s confirms the fact that their overclocking potential is astonishingly high for high-end models. We noted gains in GPU clocks of up to 30% for Radeon HD 7970 models and up to 47% for Radeon HD 7950s in comparison to their reference clocks! Even without any increase in GPU voltage, overclocking gains were 24 and 28% respectively. The gains in memory clock are also impressive with increases of up to 48%!

Of course, overclocking is a lottery on these cards and not all of them have such high capacities and when they do, theyíre accompanied by significant increases in energy consumption and noise, which is why itís so important to have a high performance cooling system to fully benefit from the available room for overclocking.

When it comes to the Radeon HD 7970s, the reference model is still the most commonly found model on the market. It is pretty effective in terms of heat reduction and extracts the hot air from the casing, thus impacting less on other components. It is however relatively noisy in load, especially when the card is overclocked. While the XFX Double Dissipation does a little bit better in terms of noise, it doesnít cool the power stage very well and increasing the GPU voltage therefore becomes inadvisable.


With a sturdier power stage and a higher performance cooling system, the Radeon HD 7970 DirectCU II is better adapted to increases in GPU voltage. It is however very big and while it does seem to have plenty of potential, its fans could be better calibrated to deal with extreme overclocking accompanied by an increase in GPU voltage.

The R7970 Lightning has been built to break overclocking records and runs an extreme cooling system that will delight professional overclockers, though it will be of less interest for the standard user. Paradoxically, the user who doesnít want to overclock manually but rather settle for the factory overclocking will make good use of the card, as long as they don't mind the relatively high noise levels.

The first Radeon HD 7950s out all use the same PCB design but differ in terms of their cooling systems. The reference Radeon HD 7950s, whether from HIS, Sapphire or other partners, are all cooled with quite compact coolers. The fact that AMD hasnít supplied this model to the press, preferring to send out a derivative of the reference Radeon HD 7970 cooler, set alarm bells ringing. Thankfully however the reference system is sufficiently effective, though it hasn't been designed for huge overclocking situations, which cause the power stage to heat up dangerously. You wouldn't expect to be able to maintain record overclockings with 'budget' models in any case.


The PowerColor Radeon HD 7950 PCS+ and Sapphire OverClock are the models to go for if you want to go in for any serious overclocking. The Sapphire OverClock cools the power stage best, allowing you to overclock it significantly without taking too much of a risk, though in no sense will the card be guaranteed. It is also a good deal quieter than more basic cards.

The PowerColor Radeon HD 7950 PCS+ doesnít cool the power stage quite as well but is exceptionally quiet in load, quieter than anything weíve ever seen at the top-end!

The R7950 Twin Frozr III is quite efficient but doesn't do as well as the PowerColor PCS+, which is quieter, and as the Sapphire Radeon HD 7950 OverClock, which offers the best noise/heat balance.


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