Help understanding GPUs and PSUs


I recently bought a GTX 285 stock settings. Upgraded from a 8800gt and have been trying to understand power requirements for GPUs.

My current powersupply is a Corsair HX-520W and while trying to figure out if I needed to buy a new PSU I have become more confused than when I began my search.

The GPUs box says a 550watt PSU with 40+ amps on the 12volt rail, I first I thought this meant I would need a new PSU but I've found three sources that tell me that the one I have now is fine. Two of the sources were very vague about the reason but the third said that the amps on the 12volt were the important part and as it was at least 350amps in all that the card would work fine with this PSU.

I'd like to know if this PSU will work and if it does I'd really like an explination of why it works. Me being a curious fellow and all. :D


Techgage Staff
Staff member
Here's the label on your PSU:

Most PSUs have multiple 12V rails, you are interested in the total available power from all 12V rails. Corsair provides this for you conveniently, 18A each (54 total) and 480 combined watts is available. As this is a good quality PSU the wattage ratings are not exaggerated, so it has plenty of power to run a GTX 285.

If you want to get even more technical, just remember watts = volts x amps ;) Take the total combined wattage (480W) and divide by the volts (12V), and you get 40 amps. So in reality, this PSU offers a combined total of 40 amps, not the 54A you get by adding all three 12V rails together.