The cards finally arrived:
These are the 'workstation edition' of the Powercolor 7990 Devil13; to the best of my knowledge we are the only customer to have these. Currently testing them with the original air coolers prior to fitting the custom nickel-copper waterblocks and integrating them all into the same machine;
Host machine has dual overclocked 8-core Xeons, 128 GB DDR3, quad SSDs, 10gig ethernet, dual PSUs, quad triple-fan radiators etc. 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; there was lots of flickering and Catalyst Control Center crashed when we disabled CrossfireX, but after opening it up again CrossfireX was finally disabled and so far dual-device tests are working fine. Will be running 8-GPU scaling and overclocking tests next week; if it works well then we will make this spec our standard developer workstation for the next project.