Good for AMD. Absolutely fail on Nvidia's part for not getting the win with GM204.
Ironically huge win for the consumers:
1) A single 980 isn't even fast enough for 4K, with most reviewers/users with real world experience recommending 290 CF/ 970 SLI / 980 SLI or faster. 5K is more than 70% of the 4K resolution which would mean essentially 3 high end GPUs. The difference between 970M/980M/295X is immaterial for modern games at 5K - ie., slideshow.
2) iMac is not a gaming platform. You just need solid rendering and 2D/3D video acceleration. AMD delivers that easily with OpenCL acceleration in the entire Adobe Suite.
3) While undoubtedly 970M/980M are more capable gaming cards and they have a more forward looking feature set, it's just mind-blowing that Apple is launching a full PC with a 5K 27" display at $2500 when Dell will charge that much for the display alone. I bet if Apple used NV they would have had to take a hit on their margins or raise the price beyond $2500. This pricing actually makes the iMac look like a bargain for someone who wants a display of this quality.
4) With shortage of GM204 desktop chips, Apple would have likely ran into a major shortage of 5K iMac if they used 970M/980M OR PC gamers would have faced even worse shortages of 970/980 cards. Sounds like a very smart decision by Apple to anticipate that NV would not have been able to meet demand for GM204 across iMac and PC mobile/desktop products.
-> Next year the iMac will be even more impressive with Broadwell/Skylake and Thunderbolt 3.0. I think if I was considering the iMac, and since a lot of users keep them for 3-4 years, I'd wait until that version.
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Apple claims 3.5 TFlops of SP. That likely suggests a 2048 SP Tonga XT @ ~850mhz. I wonder if the full Tonga XT has those rumoured 48 ROPs and/or 384-bit memory bus?
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PC monitor makers need to wake up. If Apple sells a full blown PC with 27" 5K monitor at $2.5K, we should have $1.3K 27" 4K IPS displays already, not those $3K 4K monitors like the Asus one.