On Mon, 22 Dec 1997 14:12:52 -0700 Peter Shoebridge writes: >There is a way to fool a PC power supply to work without plugging it = >into a motherboard. If I remember, it involves shorting two wires, >it's = >just which two. There's nothing special about the interface between the supply and the motherboard. Power flows in one direction, and the supply also provides an active high "power good" that in most cases resets the PC CPU but can also be ignored. There's no need to short any wires. However, most PSU's require some minimum load on the 5V output, which the motherboard would provide. This is why they don't work when not connected, with no load, the regulator can't control the output voltage and the supply shuts down. About 1 or 2A should be enough, use a suitable resistor, light bulb, etc. For example, a 3.3 ohm, 10 Watt resistor (or several hundred PIC chips) from 5V to ground should work. Up to a point, the larger the load on the 5V line, the better the 12V output will work. If your application needs primarily 12V, and very little or no 5V, it's possible to modify the supply so it regulates via the 12V output. This is rather advanced though.