My supplier carries 6 brands of HD6990 card: ASUS, Club 3D, GIGABYTE, PowerColor, SAPPHIRE and XFX.
Now I remember ever having read a review of the 5970 card, and there it was stated that for instance AMD's reference design had issues with the VRM's coolings, and that ASUS and Club 3D just copied the reference, including that particular design flaw, but that Sapphire made its own improvements.
Does anybody know if this is general behaviour of these manufacturers and which manufacturer produces the best cards for mining?
There is zero difference between the brands. They are all the same chips from AMD with reference coolers and clocks.
I would recommend XFX on the basis of lifetime warranty even if the card is overclocked or using the BIOS switch.