It also must have at least one Serial ATA power connector and support for 75 W six-pin and 150 W eight-pin graphics card connectors.

Output: A minimum of two 12 V rails as well as dedicated 3.3 and 5 V power outputs.

A current ATX 2.3 PSU has to meet the following standards:

Later revisions extended the motherboard connector to 24 pins. One of the biggest changes was the introduction of a 20-pin power connector that made it impossible to damage the motherboard by connecting the PSU improperly.

As originally implemented, it required three different sources at 3.3, 5, and 12 Volts DC, all of which fed the motherboard. The Advanced Technology Extended specification originally was introduced in 1995 as a way to ensure that PSUs would be able to support the growing energy needs of ever faster processors and more powerful graphics cards. Stable power is the first requirement of any system, as without it you'll get crashes all the time. Description HP Bestec ATX0300D5WC Rev:A 300W 24 Pin 4Pin +12V Power Supply 5188-2625

Bestec power supply atx0300d5wc