Just to be clear, this is the correct answer.
6750m/6770m are not Juniper based (Turks instead).
.No that wouldn't have been enough for that. I have to grossly guess here as far as scaling with CUs is concerned as I haven't seen a single review comparing 7770 and 7750 at the same clock (with PT+20% of course if overclocking the 7750), but I think a somewhat fair assumption would be for 20% more CUs you still couldn't expect more than a 10% increase in performance (judging by separate core/mem overclocks the memory actually seems to start limiting quite a bit if you only increase core clocks), and I think that's quite optimistic already. So with the reference clocks 12 CUs at best would have helped to catch the 6850. Likewise the Pro (which should see more of an increase because not only the difference percentage-wise is larger but also the shader/bandwidth ratio is significantly lower) would probably go from a bit slower than 5770 to a bit faster on average (and very obviously nowhere near 6850 since the current 10 CU part with much higher clocks can't even get the 6850).
I don't know if it was due to this, AMD could have fused off more CUs to still hit that target with the pro (why not have 9 CUs...), though admittedly that would only have increased the already large difference between the 7770 and 7750 (and hey I criticized some of the parts as basically non-scaling with simd count in the past so I shouldn't complain too much now that AMD "fixed" that "problem" by lowering the CU count already on the 7750, though scaling _might_ be better now). By the die shots and some pixel counting a CU is ~5mm² (though that does not include any area potentially needed outside the visible regular structure) so a 2 CU increase, while not that dramatic, definitely makes a difference with such a small chip.
12CUs at 1GHz would have a higher shading power than the 6850. In it's current form the 7770 is anywhere from 5%-11% slower (depending on the review) than the 6850 while having 16% less shading power. Basing on that and with some driver optimization, the theoritical 12CU part could have ended between the 6850/6870.
It would still have been a smaller chip than Juniper.
Well I just scaled up performance by a factor of 2 (which is about GTX 580) then subtracted a little bit to account for not perfect scaling
Could be to much for the sweet-spot ~250-260mm².
Agree, the price/performance ratio of Cape Verde is terrible. Its actually a Turks replacement which AMD is trying to push on us as a Juniper/Barts replacement..and at Juniper/Barts prices no less
I really wonder why they didnt go for a 12 CU part instead of 10. Adding 2 more CU's would have added very little to the die size, say 10 mm2. Surely the cost difference between a 130 mm2 chip and a 120 mm2 chip cant be that high. And the memory clock is on the lower side as well. Maybe they reused the old Barts MC because of the smaller size. With 20% more CU's and BW (say if it was clocked at 5.5 Ghz), the performance might have still been acceptable, and would have pushed it into the next segment. The cost increase would have been negligible.
I was actually looking forward to Pitcairn..but now i dont think i'll keep my hopes up
Edit: Also for a 12 CU part, if they launched a cut down part with 2 CU's disabled, the differnce would have been lower(16%) than between a 10 CU and 8 CU part (20%)
Yes but that's still a lot larger than Turks.
I'm not sure it's really a low-speed gddr5 design. Overclocking seems to indicate otherwise. Plus the fact that I've yet to see any amd gpu where not either the memory is overvolted or the clock is significantly lower than the gddr5 chip maximum (and here it's simply the latter), so imho the somewhat "low" memory clock speed does not indicate the controller wasn't designed to handle more (probably not 6Ghz but 5Ghz seems quite possible). Plus for the faster chips it probably makes more sense to go for the more expensive gddr5 chips anyway.
Educated guessing suggests 78xx? Though I think the specs will be a bit lower as usual, the top dog might not exceed desktop 7750 performance by much.
Good to see I'm not the only one here that thinks this way.
So I guess thats an indirect confirmation that TDP was the biggest factor
(I never meant that us forum dwellers have more insight than anyone from your group. )Yes agree. Really meant "top Cape Verde chip" there. Should definitely see some pitcairn in notebooks, but of course restricted to the big/heavy category.
