RussianSensation
Elite Member
- Sep 5, 2003
- 19,458
- 765
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It might not be slower. You are making the assumption it has the same performance or lower. It probably uses tweaked GCN shaders,appears to have greater memory bandwidth and also it probably uses boost clocks too. People judged the HD6870 and thought it would be "slower" than an HD5850 based on leaked specifications since it had far less shaders.
Ok how much faster can it be?
HD8870M
640 SP
700mhz
4500mhz GDDR5
128-bit
FP32 0.992 Tflops
FP64 0.062 Tflops
vs.
HD7870M
640 SP
800mhz
4000mhz GDDR5
128-bit
FP32 1.024 Tflops
FP64 0.064 Tflops
Even with Turbo boost and tweaks to GCN, I can't see much difference in performance. Comparing HD6870 to HD5850 is actually not making these products look good. HD6870 was one of the most underwhelming products to have come out from AMD. It launched 13 months after HD5850 and its performance was just 4-5% faster. Also comparing shaders of HD6870 to HD5850 is misleading because HD6870 was clocked at 900mhz and HD5850 was clocked at 725mhz. There were hardly any breakthrough efficiencies in HD6870, despite what AMD's marketing was spinning. It was a matter of upping clocks by 24% to alleviate the pixel fill-rate bottleneck AMD cards have every generation it seems and removing some shaders/TMUs to maintain power consumption/die size targets. The actual shader performance of HD6870 barely dropped (1120 SPs @ 900mhz = 2.016 Tflops vs. 1440 SPs @ 725mhz = 2.088 Tflops for 5850). Texture performance was also barely changed since the loss of TMUs was 22% but because of 900mhz GPU clock, this loss was largely mitigated. That was no magic, just fixing the pixel fill-rate deficiency, while minimizing the penalty to shader/texture performance. If you look at the specs of HD8870M, I am not seeing any clever tricks/rebalancing of the specs that address some particular weakness in a similarly clever way. Ya, the memory bandwidth went up, but barely.
I suppose since AMD doesn't position HD8870M as a replacement for HD7870M, then they'll say comparing HD8870M and HD7870M makes no sense as I just did, but then their marketing makes no sense.
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