I think that's fine, but it seems to me there are implications that GDDR5's clocks are scaling slowly, because engineering the GPU end is harder - to a certain extent it seems the memory chip is "relatively passive" - I don't know if that's fair though. 6Gbps chips are supposedly available. Or maybe with the disappearance of Qimonda they aren't, now.
Additionally, AMD has built something that is "2x" HD4890 but it's strangled by significantly less bandwidth. GDDR5 bandwidth, even if it gets to 7Gbps, is only about 40% higher than HD5870 will have.
A single chip with a 256-bit bus of the current architecture can't scale dramatically with that prospect of available bandwidth. And that's the best case imaginable.
It seems to me that RV770's GDDR5 implementation was a kind of baby step, hence the problems with power consumption and glitches with varying clocks. So RV870 solves those problems and is, overall, refined.
Though it has to be said, even if RV870 supported 6Gbps GDDR5, that would still be quite a constraint on overall performance.
Jawed
Yep, i knew you talked about the GPU end.
I should have been more clear about what i meant.
If i understood correctly, your interpretation about the AMD slide is that:
AMD has difficulties engineering the GPU end and scale the GDDR5 speed beyond 5Gbps (it has technical difficalties
in general...)
and my interpretation is for one parameter only:
temperature.
I mean:
AMD has difficulties engineering the GPU end and scale the GDDR5 speed beyond 5Gbps regarding only the temperature that AMD wants to maintain for the GPU core.
The old designs had
90°C and maybe AMD decided that it must do something to lower the temperature level.
It is very important for the future progression to design with such policies.
Like i said, i may misunderstood the AMD slide due to my lack of technical background.
I agree about the possibility that the 58XX is bandwidth limited (i posted about it one week before the AMD event and i was dead on that 5870 will use 5Gbps modules.
Like i said back then for me the main reasons that this is happening is because price level and volume (quantity) of the GDDR5 ICs that AMD is targeting for the 5870 SKU.
Qimonda was behind Samsung and Hynix regarding process technology (for example when Samsung was at 60nm, Hynix was at 66nm and Qimonda was at 70nm).
The thing is that Qimonda made a very good business decision to skip GDDR4 and they could compete much more effectively with Samsung and Hynix for GDDR5.
6Gbps ICs have also Samsung and Hynix.
I am not sure but i think the Qimonda ICs had better power consumption characteristics than the Samsung/Hynix ICs (same or nearly same process tech)
For me 5870 needs around 1,5GHz to show its true colors. I don't mean that with 1,5GHz will reach the level of 4870 performance/bandwidth efficiency, but that after 1,5GHz the performance improvements will be meaningless from a performance / memory scaling ratio perspective.(for the vast majority of the games at 4X AA)
Afterall 4870 had +20% clock speed and +80% memory bandwidth than 4850 and only +33% perf. (weighted average at 1920X1200 4XX AA 16X AF)
and the memory controller in the 5870 will be a new one, possible better than 4870's...)