Question about power supplies

[boxleitnerb]

This is probably a dumb question but here is it anyway:

With a power supply I have 2 12V rails, one (+) and one (-). If I want to hook up a video card that needs over 30amps (like x1900xt) to a power supply that has 17 or so amperes on the two rails respectively, would that work? do I just have to add 17 and 17 together or is only one rail for the vid card?

[maaoouud]

More is probably better. Use one of those 2x 4pin molex -> 6 pin pci-express adapters and connect one molex to each of the 12V lines (not both to the same cable coming out of the power supply). 17amps (~200W) is probably enough with only one cable connected though -if you only use that rail for the x1900xt.

[Xmas]

The -12V rail is usually far weaker (maybe around 1A or so), so that won't work.

[Basic]

The -12V rail is usually far weaker (maybe around 1A or so), so that won't work.

Not to mention that +12V is not -12V, and connecting them will quite possibly fry the PSU.

Even if you had two separate +12V sources, it's usually not a good idea to connect them directly. That's because there is a small varation in what different PSUs think is 12V. This result in an uneven loading, and one PSU could be overloaded while the other hardly outputs anything.