Sapphire HD 7950 OverClockSapphire 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 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.
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
[ 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 isn’t only well-cooled, it’s 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
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.