SLI GTX460's at 900Mhz - Complete System Freeze up in-game

[chris89]

These are GR23P cards with 1 6-pin. They stock clock at 650Mhz at 0.950V.

I added heatsinks to the all voltage regulators on the card. When it freezes it's only hitting each gpu at like 40% and only 60C each.

At 900Mhz and 1.125V is usually stable, but I bumped them up to 1.150V and it still freezes. Did a complete driver wipe with Display Driver Uninstaller, then installed 340.43's Win7 X64.

Just wondering why it freezes? Usually the driver crashes but these complete system freezes confuse me. I did a 10 hour Extended memory test in the Windows Memory Diagnostic.

I also ran 50 runs of Extreme IntelBurnTest at max ram and it passes every time.

Maybe someone out there can give some in-sight? I had these stable at 900Mhz at 1.125v for a long time, now it's just freezing all the time...

*UPDATE*
Fixed it. Ended up needing 1.5v on the IOH PCIE, and 1.5v on the ICH PCIE. On top of 1.5v on the QPI, and 1.475v on the Cpu vcore. Then had to set the damn IOH (Northbridge) to 1.25v.

Tested the cpu on intelburntest, and the gpu's at 100% load. Totally stable. CPU Core #1 hit 87C, GPU's were at 80C. Hot and Stable as STUFF. I let it sit for 4 hours at full load to ensure stability.

Main issue may of been that I had the GPU's at 1800Mhz memory rather than 1700Mhz memory. Set it to 900Mhz core clock, 1800Mhz Shader, 1700Mhz memory @ 1.125V. Performance is awesome.

I'm seeing a bit of droop on my 1000 watt power supply down to 11.872V from base of 12.264V. Will need to get a fatter EPS 8-PIN extension at 16 AWG to maintain 12v under load. Not only that but I need a fatter AWG power cord. Will need a 12 AWG power cord to the power supply as well. As well as keeping that 12 AWG at 12" or Less.