Power supplies are a critical, often overlooked component when building your rig. As high-end dual-graphics cards pull more power, they're creating headaches for power supply manufacturers. When we were writing our recent socket 939 motherboard mini-roundup, we wanted to test how the system would run with two high-end graphics cards installed. We began with a system that had a Silverstone SST-ST65ZF PSU. This power supply is rated for 650 watts, and is SLI certified by Nvidia. So we fired up an Nforce4 SLI X16 system with two 512MB graphics 7800 GTX graphics cards and an Athlon 64 FX-60. About halfway through the 3DMark06 run, the system shut down. There was no warning, no smoke, no heat. It just turned off. After some grumbling we tried swapping out memory and changing out the CPU. No effect. So we finally switched the power supply to a PC Power & Cooling Turbo-Cool 850 SSI. At that point, it all ran just fine. We were in a rush to wrap up benchmarking the motherboards, so just chalked it up to a bad power supply and moved on.

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