| BlueFalcon said: I posted this in another thread but I thought it's worth of consideration in this thread too. DDR3 of Xbox 720 vs. GDDR5 of PS4 - the impact on the GPU performance. |
Your comparisons are pretty off the GT640 is going from 28.5 GB/s for DDR3 to 80GB/s for GDDR5 for example, there are no DDR3 cards on the market that offer anywhere near 68GB/s and even if they did the comparison still wouldn't work as the Durango has the ESRAM and also aparently some new memory controlers that allow the GPU to access both pools at the same time. Also keep in mind Orbis will likely be limited to a 128-bit Bus (wider Buses get exponentially more expensive and can limit die shinks in the future) so is probably looking at ~86GB/s (highest I have seen for GDDR5 on a 128-bit bus) it's self so will likely not be some bandwidth monster ether.
As long as you can fit the framebuffer in the eSRAM the main memory bandwidth shouldn't impact ROPs too much, especially as the GPU can access both pools at the same time. And with a modern tile based renderer you can swap out tiles as needed so the don't even need to fit all the render targets in eSRAM at once, just like what devs do with the X360s 10MB framebuffer today. It's still a bottleneck in many cases but not one that couldn't be worked around with the eSRAM even if it means dropping the native resolution a bit.
@TheVoxelman on twitter
