What's powered by -5V?

**Gutter** · 06-20-2004, 02:53 PM

I picked up a tiny (5W x 4D x 3H) 120W powersupply from Goodwill just a little bit ago noticing that it didn't have a -5V pin. What components (on-motherboard or peripheral) use -5V?

**eugenen** · 06-20-2004, 09:59 PM

nothing much anymore. Its left over from the original PC and I have heard of it being used once or twice in a sound card but your chances are good that you can run fine without it.

**starfox** · 06-21-2004, 12:16 AM

I think -5V is used on the old ISA bus, and not used very often any more.

Apparently the -12V is used for serial ports, and not much else either.

**stevewm** · 06-21-2004, 11:56 AM

-5v is not used at all. Nethier is -12v on modern motherboards.

The RS-232 serial port drivers (built into the southbridge these days) on pretty much all motherboards today create their own -12v.

I've seen some very cheap off brand boards even go wthout -12v at he serial port. Instead of swinging +12v (binary 1) to -12v+ (binary 0) they go +12v (binary 1) to 0v (binary 0).

Fortunately most serial port equipment is very forgiving and will accept 0v as binary 0.