Although the Radeon HD 7950 still has a 384 bit memory bus and 32 ROPs, AMD has taken the opportunity of reducing the number of processing units and texturing units. Four of the 32 groups of 64 processing units and 4 texturing units have therefore been deactivated, which gives us 1792 processing units and 112 texturing units in all. With the clock dropping from 925 to 800 MHz, the overall reduction in processing power compared to the Radeon HD 7970 is 24%, while there was only a 16% drop between the two Radeon HD 6900s. The gap in terms of memory bandwidth is however identical for both generations: -9%. Note also that over the last year the memory clock hasn’t changed, which is unusual.
In comparison to the Radeon HD 6970, the Radeon HD 7950 gives slightly lower triangle and pixel throughput but slightly higher processing and texturing power. The memory bandwidth is however higher: + 36%.
The Radeon HD 7950 presss edition
For this test, AMD supplied us with a ‘reference’ 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 you’ll find in stores from certain partners. To our knowledge, the card supplied by AMD to the press will not be put on sale and is therefore not representative of the final product that you’ll find in stores. This isn‘t the first time that AMD have tried such a manoeuvre, which is regrettable. Here however is what the test sample looks like:
The Radeon HD 7970 and this Radeon HD 7950 are in the same format as the Radeon HD 6970: double slot and 27.5 cm long. Its cooling system is similar but has been slightly modified. 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. It’s therefore no longer necessary to send some of this hot air into the casing above the card but one of the two DVI ports has therefore 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. 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, we’re 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. Truth be told this increase in power isn’t really necessary: the Radeon HD 7970 makes do with five of these phases for a TDP of 250W and the Radeon HD 7950 with four 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 from the 8+6 set-up on the Radeon HD 7970 to 2x8 pin power supply connectors for the Radeon HD 7950.
While the Radeon HD 7970 uses Hynix ROC GDDR5 memory certified at 1.5 GHz, the Radeon HD 7950 makes do with the T2C version of the same memory, certified at 1.25 GHz.
Two CrossFire X connectors are still available to ensure tri and quad-GPU support, as is the dual bios switch allowing you to return to the original bios.