A 400-watt switching FSP200-60SV PC Power Supply will not necessarily use more power than a 250-watt 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 250-watt supply if you have 250 watts total in devices, since the supply should not be loaded to 100 percent of its capacity.
According to PC Power & Cooling, Inc., some power consumption values (in watts) for common items in a personal computer are:
Accelerated Graphics Port (AGP) card = 20 to 30W
Peripheral Component Interconnect (PCI) card = 5W
small computer system interface (SCSI) PCI card = 20 to 25W
network interface card = 4W
50X CD-ROM drive = 10 to 25W
RAM = 10W per 128M
5200 RPM Integrated Drive Electronics (IDE) hard disk drive = 5 to 11W
7200 RPM IDE hard disk drive = 5-15W
Motherboard (without CPU or RAM) = 20 to 30W
550 MHz Pentium III = 30W
733 MHz Pentium III = 23.5W
300 MHz Celeron = 18W
600 MHz Athlon = 45W
FSP200-60SV PC Power Supply 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.
Power Supply Improvements
Recent motherboard and chipset improvements permit the user to monitor the revolutions per minute (RPM) of the power supply fan via BIOS and a Windows application supplied by the motherboard manufacturer. New designs offer fan control so that the fan only runs the speed needed, depending on cooling needs.
Recent designs in Web servers include power supplies that offer a spare supply that can be exchanged while the other FSP200-60SV PC Power Supply is in use. Some new computers, particularly those designed for use as servers, provide redundant power supplies. This means that there are two or more power supplies in the system, with one providing power and the other acting as a backup. The backup supply immediately takes over in the event of a failure by the primary supply. Then, the primary supply can be exchanged while the other power supply is in use.