How PC Power Supplies Work

How PC Power Supplies Work

Power Supply Wattage

A 400watt switching power supply will not necessarily use more power than a 250watt supply. A larger supply may be needed if you use every available slot on the motherboard or every available drive bay in the personal computer case. It is not a good idea to have a 250watt supply if you have 250 watts total in devices, since the supply should not be loaded to 100 percent of its capacity.

Accelerated Graphics Port AGP card = 20 to 30WPeripheral Component Interconnect PCI card = 5Wsmall computer system interface SCSI PCI card = 20 to 25Wnetwork interface card = 4W50X CDROM drive = 10 to 25WRAM = 10W per 128M5200 RPM Integrated Drive Electronics IDE hard disk drive = 5 to 11W7200 RPM IDE hard disk drive = 515WMotherboard without CPU or RAM = 20 to 30W550 MHz Pentium III = 30W733 MHz Pentium III = 23.5W300 MHz Celeron = 18W600 MHz Athlon = 45WPower supplies of the same form factor form factor refers to the actual shape of the motherboard are typically differentiated by the wattage they supply and the length of the warranty.