My 850W PSU is not Enough for Two GTX 480 Stressed by EVGA OC Scanner

EVGA OC Scanner and GTX 480 SLI
Just before the PSU shutdown 😉 – SLI visual indicator enabled…

I took the time this morning to test a 2-way SLI of GTX 480. For two reasons:

  • 1 – because it’s a geeky stuff 😀
  • 2 – to test the new SLI profile that has been added by NVIDIA in the R257.15 for EVGA OC Scanner.

The cool thing with EVGA OC Scanner is that it has now a SLI profile in latest NVIDIA drivers. No longer need to rename the exe in etqw.exe (you can even use that SLI profile for FurMark 😉 ). If you have a SLI system, just run the OC Scanner in fullscreen (fullscreen mode is fundamental for SLI) and you’re okay!

That’s what I did… 1920×1080 fullscreen with the power draw unlocked… and I got a nice shutdown after one second.

Hummm… I don’t know why but I was sure that my PSU was the weakest link of my testbed (CPU = Core i7 960). This kind of shutdown is symptomatic of a too high power consumption. I thought my 850-watt PSU was enough to feed my testbed but I was wrong.

Antec TPQ 850W PSU
my Antec TPQ 850W PSU

That’s why I added in the OC Scanner a way to control the power draw via a simple delay in the rendering loop (I called it tone down delay). By default the tone down delay is equal to zero. If you increase the value, let’s say tone down delay = 20, the rendering is stopped during 20 ms. And you can increase or decrease the tone down delay as you want.

The tone down delay has allowed me to confirm that my PSU was not enough powerful to feed two highly stressed GTX 480. I started EVGA OC Scanner in 1920×1080 (power draw unclocked) with a tone down delay of 50ms and I decreased it until I reached the PSU shutdown (the shutdown occurred for a delay lesser than 16ms).

Conclusion: you must have a 1000W or better a 1200W PSU for enjoying a 2-way SLI of GTX 480! I hope I’ll able to check that assumption shortly…

This tone down delay will be available in MSI Kombustor too…