I am running an Asus M4A785TD-V EVO motherboard with AMD Phenom II 955x4 3.2 Ghz processor, 4Gb Corsair DDR3 1066 memory and a BeQuiet! 650 power supply, and running 64-bit Windows 7. BIOS set to automatic. The system is inherently ustable. It has no specific one problem, but the system variously hangs, runs slowly, parts of the operating system stop working, the screen goes blank, memory errors are displayed, etc. Memory tested ok. SANDRA showed that the -12 volt supply was only -8.91 volts. All other voltages were fine. I replaced the power supply. Still - 8.91 volts. I then tested the new power supply in my old computer and SANDRA showed -12.01. I concluded that the problem was the motherboard so replaced that. However, new motherboard also showed -8.91 volts on the -12 volt supply, and has the same instabiltiy problems. Can it be that both motherboards have the same fault, or am I missing something?