The Radeon 7990s finally arrived, have been trying to get hold of them for months :
These are the 'workstation edition' of the Powercolor 7990 Devil13, which ship without all the pack-ins the consumer version has but are otherwise identical. Currently testing them with the original air coolers prior to fitting the custom nickel-copper waterblocks and integrating them all into the same machine;
These workstations have dual Xeon E5-2687Ws with a mild overclock (2 x 8 core / 3.2 GHz / 20 MB cache), 128 GB DDR3-1600, quad SSDs (Kingston MAX-IOPS) in RAID 0, triple 4TB HDDs in RAID5 for backup, dual 10 GBASE-T ethernet (plus motherboard dual gigabit), dual 1.2 KW PSUs, touchscreen system management display on the front, watercooling with two Laing D5s + four triple 120mm radiators etc. Originally planned to use the EVGA SR-X as the motherboard - our previous gen GPU workstations used the SR-2 - but the horrible PCIe setup (lanes on 2nd CPU not used), asymmetric memory setup and cheap & nasty RAID controller forced use of the Asus Z9 PE-D8 WS instead. The first prototype used 7 Radeon 7970s with AquaComputer slimline waterblocks and the MAX-7 manifold; these was a nightmare, constantly leaked and shorted out even after a lot of effort to replace screws, seal gaps and insulate metal. For the second prototype we've switched to quad 7990s with custom waterblocks from EK.
I can happily confirm that the 'impossible to disable crossfire on dual-GPU cards' bug that made the 5970 and 6990 unusable for GPGPU has been fixed for the 7990. The 7990s seem to be working exactly like two 7970s with scaling in excess of 90% for simple two-device OpenCL tests. Will be mounting the waterblocks and doing 8-GPU & overclocking tests next week.
I sincerely hope EVGA fix the issues with the SR-X in their next dual socket board, so we can go back to them for future generations of our GPGPU workstations.