The ATI Radeon 5XXX Thread

[hurleybird]

jaredpace: I find that surprising, but how does that explain good performance gains from OC'ing DDR5 speeds in 4870, if it's so much over the bottleneck?

What good performance gains?

This is addressing comments about memory bandwidth. The hd4870 has 115gb/sec gddr5 memory, if you take the 4850's limited 64gb/sec memory bandwidth and apply it to the same clocked 800 shaders of the 4870 (750mhz ie an overclocked 4850) you only lose about 5% overall performance compared to the stock hd4870.

how much of that is due to bandwidth saturation, and how much of that is due to latency? All else being equal, GDDR3 outperforms GDDR5 at equal Hz.


In any case, we'll just need to wait and see. After we have the cards in hand it won't be hard to see if core and memory performance is balanced. Maybe it's imbalanced because AMD is planning on debuting faster models with faster memory. Or maybe we'll finally see some kind of shared memory on X2, and the bus AMD is using between memory controllers would be oversaturated (as well as having less space along the edge of the chip for it to fit on) with a larger memory interface. Maybe they've done some tweaking so they make better use of bandwidth? At the very least the enhancements from RV740's memory controller will be brought over. For all we know RV870 could use tile rendering! One more day.