Yea, I remember the talk about multiple GPU's becoming the future, at least on AMD's part. So where does that put Vega chips exactly? If this whole 480 X-fired deal was to be true then the Vega chips should be plenty faster than the P10 chips crossfired, or the somewhat poor scaling (in those "leaked" 3D11 benches) is intentional so that this CF deal slots right under Vega. I don't know really, this speculation is getting out of hand, and I'm annoying myself and probably others.
Vega is almost identical to Fury X in hardware (4096 shaders, HBM2 instead of HBM). There's no reason why they can't do a dual Vega too with the price adjusted to match. They can easily market the dual Polaris card as the budget VR card and dual Vega card as the performance VR card. Dual Polaris should be better at VR than a single Vega. They would likely be priced about the same with the latter being marketed towards 4K or Eyefinity gaming rather than VR.
I don't know how well 3D Mark handles multiple cards. If it is relying on Crossfire (which the "CF" would imply), 3D Mark likely isn't optimized for D3D12/Vulkan multi-GPU support. Considering previous testing was done with Ashes of Singularity, my guess is no. That 3D Mark benchmark, therefore, is likely close to a worst-case-scenario (ye olde, driver-implemented Crossfire) for a dual Polaris. It does not reflect the future of the multi-GPU technology.
2 x Fury X = 58% improvement over single using D3D12 multi-GPU in Ashes of Singularity
2 x Polaris 10 C7 = 43% improvement over single using Crossfire in 3D Mark
15% may not sound like much but if it was linear and translated to a D3D12 multi-GPU version of 3D Mark, 2 x Polaris 10 C7 would have gotten 28,535 which lands just above GTX 1080.
That said, 3D Mark only has a D3D11 benchmark which NVIDIA has a home-field advantage. Too bad we don't have any numbers for D3D12 Polaris.
This logic is flawed for two reasons:
1) 3D Mark only does as high as D3D11. GeForce has a tremendous advantage in D3D11 so the graph is intrinsically biased towards NVIDIA from the start.
2) Multi-GPU (non-driver implementation) requires D3D12 or Vulkan. Ashes of the Singularity was used for multi-GPU benchmarking. The numbers quoted above are correct.
As far as I know, there are no D3D12 Crossfire benchmarks available to guage how multi-GPU does compared to Crossfire. Further, assuming any of this has any bearing comparing D3D11 to D3D12 between vendors is simply foolish.
3D Mark 11 is a worst-case scenario for Polaris (because GCN has never been great at DX11) and multi-GPU (because it relies on ye olde driver-implemented Crossfire/SLI). Put the two together in a D3D12, dual Polaris 10 situation and I think the card would run away from GTX 1080.
Let's focus on Ashes of the Singularity:
DX11 versus DX12 = 7% boost for GCN
http://wccftech.com/nvidia-gtx-1080-async-compute-detailed/
D3D12 Multi-GPU versus single = 58%
http://www.anandtech.com/show/9740/directx-12-geforce-plus-radeon-mgpu-preview
Combined D3D11 single-GPU -> D3D12 multi-GPU = 65%
18,060 points (3DMark 11 single-GPU) * 1.65 = 29,799 points (theoretical 3DMark 12 multi-GPU)
And remember, this is throwing out the GCN async compute advantage because GeForce is terrible at it. Add in async (because what true D3D12 test wouldn't use it?) and dual Polaris 10 easily tops 30k (31,786 to be exact). If we adjust GTX 1080s scores to D3D12 + async, it's score would fall to 26,983 points.
I think what C4 is what LIKELY WAS (they might rename it though) Polaris 10 - 480 and C7 is/was 480x.
I doubt C4 could be Polaris 11 (given it consumes MUCH less power and that they've officially demoed Polaris 11 vs 960 with capped 60fps)
I'm thinking:
RX 480 = C7 CF
R9 480 = C7
R7 470 = C4
All three are Polaris 10 because
Polaris 11 is 67FF.