I can't believe people are still discussing what the 6750 and 6770 will have. Specs are already out.
Also any thinking that 6870 will be 512 bit bus is laughable. I'd seriously take a bet with someone who believed that one. 384 bit I doubt and still think 256 is what we will see.
if you stick with 256bit bus most likely you will stuck with 48rops
if you stick with 48 rops you will have to go 384bit bus
since both amd/nv had stuck with max rop per bus will be impossible to push rop further without more bus. and cayman will not have same number of rops like barts had as it's
pointless to add more shader without larger rops operate. so 48 rops has to be 384bit bus. and amd will not go odd config like nvidia and 64 rops cannot put on exist 256bit bus. 32rops on cypress = 8x4 and each rop obtain 32bit bus and that is the minimum limitation that allow ring bus to operate and cannot go below 32bit per rops. which that is the reason why evergreen line was hugely bottleneck that people tend to argue cypress was double of r770 but end up only increase 60%. original r600 are 64bit per rops and r770 are also 64bit/bus until evengreen tweak it to 32bit per rop/bus. it will be impossible to have 64rops on 256bit bus and it will end up each rops only obtain 16bit bus which existed architect won't allow it happen.
however continuing exist 32rops configuration is just pointless because adding shader don't increase frame rate, rops does. also 480 ALU is already the limitation in exist 40nm fabrication and amd won't waste such number of ALU core on only 32rops GPU.... if you know nothing about gpu architecture you better be silence because that will just make you look bad.
Yea there were some early rumors about 384 bus but with the GPUz shot I really doubt anything else now. Besides a 512 bus adds way, way too much to the cost of the board compared to a 256. No reason adding to the cost of a board when you can get the same bandwidth through higher speed Gddr5. Plus it is possible to drive the cost of that high speed ram down with bulk selling.
then you can't add more rops if you can't have higher bus...exist ringbus architect on both NV/AMD can't allow config like 16bit /rops exist. 32bit/rops is most likely the limitation that ringbus can hold. if amd insist stay on 256bit bus they most likely stuck with 32rops and there for 32rops cause bottleneck to larger number of ALU/shader as frame rate will not increase in largely margin. we all laern from how r770 was bottle neck so much by its rop then why amd want to go on narrow rops/bus if the framerate won't go up in higher number? without higher fillrate shader are pretty much useless.....
256bit bus and you will stuck in 32 rops....
with you on the us width. my guess is 256bit with higher performing GDDR5 modules than the 67X0's. Though its not long now until all is made clear. Can't wait for the NDA to be lifted
then cayman will stuck at 32 rops....
