AMD finally managed to launch the Radeon HD 7950 (the card down from the 7970) three weeks later than originally scheduled: several units less and with lower clocks but the promise of significant overclocking potential. Is this the end for the GeForce GTX 580? This is what we’re going to find out in our full analysis of this Radeon HD 7950!
Is 28nm too variable?
The Radeon HD 7950 uses the same GPU as the Radeon HD 7970: Tahiti. It supports all the latest technologies including DirectX 11.1, PCI Express 3.0 and OpenCL 1.2 and introduces a new forward-looking architecture and has been modified to increase processing unit efficiency. You can find all the details on Tahiti in our report on the Radeon HD 7970
This GPU is also the first to be produced using TSMC’s 28nm manufacturing process that introduces the use of the higk-K metal gate (HKMG). To recap, this technology was developed by Intel over four years ago to combat current leaks at transistor level without negatively impacting on performance. Competitor foundaries appear to be finding it quite difficult to integrate the technology, which explains why it has taken them so long.
It is probably the introduction of this 28nm HKMG fabrication process by TSMC that explains one of the advantages being highlighted on the Radeon HD 7900s: namely their overclocking capacity. We were able to confirm this, in particular in our test of an XFX model (article in French)
which proved to have very significant overclocking capacity, something that is unusual on a high-end GPU.
While skillfully presented as a positive by AMD, this gift to overclockers wasn't of course deliberate but no doubt comes from certain manufacturing issues which have resulted in an unusually high variability in production. There wouldn’t be any reason not to sell these GPUs at higher reference clocks if this wasn’t the case. We imagine that the high variability means that AMD has had to introduce a higher margin for error than it would like in order to ensure that enough samples qualify to go on sale. On the Radeon HD 7970, with its thermal envelope of 250W, AMD has thus had to made do with 925 MHz. For the Radeon HD 7950 the thermal envelope is 200W and the clock 800 MHz.