AMD Cayman info (or rumor)

[paulhamm]

Just a bit of fun with numbers. Caymen uses 90% of the die area for 4sps that Cypress uses for 5sps. Check the slides if you doubt. I used barts as a reference.
Cypress 334mm2 1600sp 256bit mem
Barts 255mm2 1120sp 256bit mem
Caymen ???? 1920sp 256bit mem
GF100/GF110 550mm2 512cuda 384bit mem
GF104/(GF114) 368mm2 384cuda 256bit mem

Die area estimates just for fun. Yep they have long WAGgy tails.
Caymen 334mm2/(1600/5)*(1920/4)*.9=450.9mm2
Caymen 334mm2/1600*1920=400.8mm2
Barts 334mm2/1600*1120=233.8mm2
Better Barts 334mm2/1600*1280=267.2mm2 What if HD6870 is a cut down Barts?
Barts reference accuracy 233.8mm2/255mm2=0.9168
Better Barts reference accuracy 267.2mm2/255mm2=1.0478

Barts is a significant refinement over the previous evergreen products. In the HD6870, Barts generates about 93% of the performance of the HD5870 Cypress while using less than 73% of the shaders. The question is how much of the gain in efficiency came from modified sps and how much came from a redesign of the uncore? It does seem clear that Cypress was sp heavy. That is Cypress has more sps than it can effectively use. Barts is the result of examining the evergreen products and finding ways to more effectively use the whole of the gpu.
Caymen XT should have an effective 50% performance advantage over a similarly clocked Cypress excluding performance enhancements to the uncore. AMD is showing in the various slides that the uncore changes in Caymen are even greater than those in Barts. Another question,,, is 4d=5d? We do not know, though AMD likely does. It does seem that 4d must be at least 90% as fast as the old 5d and likely more. The reason is that AMD only gains 10% die area with the change. If they did not see a potential gain then making the change would be valueless. I believe 40% better performance than the HD5870 would be a rather conservative estimate for the Caymen XT (HD6970). Depending on how well AMD has addressed the bottle necks of the evergreen (Cypress) gpu it could be that the HD6970 will be 60-70% faster than the HD5870. Pricing will be commensurate with actual performance. Expecting anything else would be silly, AMD is not a charity.
Should not be more than 3 weeks and we will know.