I am running 4 XFX 7959 Double D's on one of my rigs.  They run hot and like crap with the stock bios.  You can download your bios and go to the litecoin fourm.  Stilt will optimize it for a donation.  Memory is bottle necked on the cards with the stock bios.  With the newly fixed up bios, the cards are monsters.  My cards now run at 615 kh/s and at 70-72c, no external fans.  Rig is pulling around 1075w from the wall.

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