erm, no, actually nvidia were the first to announce that kepler and fermi would not have full support for DX12, where as AMD just said that "all GCN cards will support DX12" without saying which cards might or might not have full support
the point people were picking up on was that nvidia said fermi onwards would have basic support, so 480 onwards, where as for AMD users it is GCN only, so not as far back
Which hardware will be DX12-compatible? AMD said all of its Graphics Core Next-based Radeon GPUs (i.e. Radeon HD 7000 series and newer) will work with the new API. Nvidia pledged support for all Fermi, Kepler, and Maxwell (i.e. GeForce GTX 400 series and newer) parts. The keynote included a demo of Forza 5 running in DirectX 12 mode atop an Nvidia GPU. Finally, Intel said the integrated graphics in its existing Haswell processors will also have DX12 support. All in all, Microsoft estimates that 100% of new desktop GPUs, 80% of new gaming PCs, and 50% of PC gamers will be able to take advantage of the new API.
GCN is HD7000 series onwards, Nvidia's first statements mentioned nothing about limits, just flat out said Fermi onwards, which is a full generation earlier than AMD(gtx 480 direct comparison card was a 5870).
They were also banging on and on about having a huge market share of DX12 gpu's ready for DX12 launch, blah blah blah. They were very much talking the "everything for years will support it" route from day one. Later on they were like "oh yeah, support.... well, kinda". After they big announcements.
http://blogs.nvidia.com/blog/2014/03/20/directx-12/
direct from Nvidia, "DX12 on all DX11 gpus Nvidia has shipped".
From what I can tell, Nvidia wasn't really talking about what Kepler couldn't do in DX12 till Maxwell was released.
Oh, and btw...
http://www.extremetech.com/gaming/1...ption-by-50-boosts-fps-by-60-in-new-tech-demo
Nvidia's IGPU, using DX12 reduced power by 60%, all cpu side saving, because there is vastly less work being done. But sure, that 50W increase came directly from the CPU... working hard before to after, we all know an 80W cpu uses almost nothing then magically uses 50W more, all under load.
The fact that we can see Maxwell using more power under GPGPU loads than gaming(ostensibly DX11 based) loads. It's totally the CPU using way more power.
Again a gpu that is so much less efficient it uses supposed 100W more, is still only using 14-19W more with everything else in the system being the same.