Originally posted by: Idontcare
Originally posted by: dguy6789
The limitation on the 5870 is most certainly memory bandwidth. Memory bandwidth is the only category in which the 5870 does not outclass the 4870x2 in.
Radeon HD 5870:
Pixel Fill Rate: 27200 MPixels/sec
Texture Fill Rate: 68000 MTexels/sec
Flops: 2720 GFLOPS
Memory Bandwidth: 153.6GB/sec
Radeon HD 4870x2:
Pixel Fill Rate: 24000 MPixels/sec
Texture Fill Rate: 60000 MTexels/sec
Flops: 2400 GFLOPS
Memory Bandwidth: 230.4GB/sec
I would think this theory would be fairly easy to test and either prove or disprove by anyone who has the 5870 in hand.
Just underclock the memory. Do stock, underlocked mem by 10-15%, underclocked mem by 20-30%, and plot the benchmark data.
If you get a linear line with nice R^2 and the slope is nice and large (slope of 1 on a % bandwidth delta versus % fps delta would be perfect) then you can easily conclude the performance would be improved by having higher bandwidth above stock.
What is interesting is that no one seems to have done this test in their reviews yet (or did I miss it?).
What would be even more interesting is if the data proved out this theory as surely AMD would have tested this and determined whether or not bandwidth was really going to be the limitation of the 5870 well before the launch. So why would they artificially handicap the 5870 by knowingly starving it of bandwidth? I don't think we should assume ignorance on their part here.