I have 17X7990 in total. The core/memory voltage and frequency vary because every GPU is different. For some GPU, I can run 0.99v, with 950/1000 MHz, temperature is 70C. For others, the temperature is 85C, with 0.95V, 870/900 MHz. It depends on the position of the cards in a PC case.
I use powered PCIE risers in open case, I put extra fans to extract heat out.
The original thermal past is extremely thick. I tried to apply thin layer of thermal paste, the improvement is minimal, just 2-5 degree, as the heat sink cannot touch the GPU evenly, even after I adjusted the force with the 4 screws. That could be the reason why manufacturer apply a thick layer of thermal paste.
whats the maximum number of 7990 gpu's we can run per motherboard, can you please send me your configuration, specs of the rigs etc, I have 10x7990 cards that I am looking to put maximum per motherboard. if you can some pics would be great too. Thanks
I run 4X7990 or 2X7970+3X7990. These are all 8 GPU in total. I have not tried more than 8 GPU.
The MBs are ASUS Rampage Extreme (too powerful for mining), MSI Z77A GD55, Gigabyte GA-Z68AP-D3, ASUS P7P55D pro. These MB have 5 PCIE slots or more.
I use Windows 8, Catalyst 13.4 or higher as lower version does not recognise 7990. Some MB needs 13.8 or higher. I do not know why.