Hello, I have a 2x HD6950, default bios, in crossfire configuration on an X58 MB and an i7 920. I tested the card separately and each card is able to reach gpu 880MHz and ram 1325 MHz (i didnt go further). My power supply is a 650W efficency 80+. Drivers installed are the latest at the moment i'm writing (10.12a). Everything at stock speed/settings. Problem: I have some "Drivers stop responding" in crossfire configuration when i run 3d applications. I assume this is related to the Wattage of psu. Windows is working without any problem in Aero. It's even more strange that i was able to run 1 complete benchmark run in 3dmark11, then i rebooted and started the problem, crossfire was on (P7800 score). The TDP of a HD6950 is 200W, i set the Power Control, for each card, at -20% so it should be around 160W, an i7 920 has 130W TDP (benchmark and games cant reach that cpu usage). The total TDP is 450W and TPD means maximum amount of power (even 99% load doesnt necessarily mean the aximum power absorbed). Since my PSU is 650W and the TDP is 450W i assume i have about 200W free for the motherboard (50W?), 1 hard drive (30W), 1 cpu cooler fan, usb mouse and keyboard. I'm start thinking i got scammed with the PSU... I will be able to replace my PSU in 20 days after i move (my luggage is already too heavy for the flight company) but the RMA will be a pain from my new location. Having a look around i found some ppl reporting the same behave of my cards/drivers in crossfire with 1000W PSU. Anyone else having this kind of problems? Thanks.