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Roundup: the Radeon HD 7970s and 7950s from Asus, HIS, MSI, PowerColor, Sapphire and XFX
by Damien Triolet
Published on May 9, 2012

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 isn’t 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 aren’t 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 don’t 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 XFX’s 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 °C 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 isn’t really any more efficient than the reference system. It’s a little less so at idle and similar in load. It is however better calibrated as far as we’re 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 won’t do as well for you, but if you have a very well ventilated casing, it could do better than it did in our tests.

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