apoppin wrote:Not true. AMD is almost TWO YEARS LATER than Nvidia in giving us the answer to Fermi and GPU computing
- Don't you think they might have had a little extra time to work on it? And it is still not impressive as it should be for a generational change on a full node lower. As Ryan said, performance wise it is "acceptable". Not stellar.
All true. My review would have shown some DX9 games where the HD 7970 does not look quite so impressive. AMD could not afford that.
However, AMD Graphics will not talk to me any longer. And i now realize that i provoked them by posting at ATF.
As AMD has decoupled the ROPs from the memory controllers in its GPUs it can deactivate ROPs without affecting the memory controllers. The ROPs do however take up a lot of memory bandwidth and also represent an important pathway for this memory. Deactivating half of them therefore does have an impact on the GPU’s capacity to exploit fully the memory bandwidth made available by the 256 bit Barts bus.
The real reason HD7970 is 40% faster than HD6970 is not because GCN is magically better in games than VLIW4, but because:
- HD7970 has 40% more shader performance (925mhz x 2048 SPs vs. 880mhz x 1536 SPs)
- HD7970 has 50% more memory bandwidth (264 vs. 176)
- HD7970 has 40% more texture performance (128 TMUs @ 925mhz vs. 96 TMUs @ 880mhz)
There is no evidence at all that shows that each one of 2048 GCN shaders is more efficient than 1536 SPs of VLIW-4.
The performance increase is almost exactly linear with increases in specifications. That means GCN ~ VLIW-4 for games today, with a significantly larger boost in GPGPU compute. Basically GCN provided no loss in gaming efficiency, but it didn't improve efficiency for games either, at least not in today's game engines. Perhaps in the future DX11 engines, that may become true.
We are also hearing that across the board, the stock HD 7970 is a bit disappointing as it only scores about 20-30% faster than the stock GTX 580 – well within reach of an overclocked GTX 580 and priced similarly at about $550.
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