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Overloading the Power Supply

The biggest cause of power supply overload problems has historically been filling up the expansion slots and adding more drives. Multiple hard drives, CD-ROM drives, and floppy drives can create quite a drain on the system power supply. Be sure you have enough +12v power to run all the drives you plan to install. Tower systems can be especially problematic because they have so many drive bays. Just because the case has room for the devices doesn't mean the power supply can support them. Be sure you have enough +5v power to run all your expansion cards, especially PCI cards. It pays to be conservative, but remember that most cards draw less than the maximum allowed. Today's newest processors can have very high current requirements for the +5v or +3.3v supplies. When selecting a power supply for your system, be sure to take into account any future processor upgrades.

Many people wait until an existing component fails to replace it with an upgraded version. If you are on a tight budget, this "if it ain't broke, don't fix it" attitude might be necessary. Power supplies, however, often do not fail completely all at once; they can fail in an intermittent fashion or allow fluctuating power levels to reach the system, which results in unstable operation. You might be blaming system lockups on software bugs when the culprit is an overloaded power supply. If you have been running your original power supply for a long time and have upgraded your system in other ways, you should expect some problems.

Although there is certainly an appropriate place for the exacting power-consumption calculations you've read about in this section, a great many experienced PC users prefer the "don't worry about it" power calculation method. This technique consists of buying or building a system with a good-quality 300-watt or higher power supply (or upgrading to such a supply in an existing system) and then upgrading the system freely, without concern for power consumption.


My preference is the 425W supply from PC Power and Cooling, which is probably overkill for most people, but for those who keep a system for a long time and put it through a number of upgrades, it is an excellent choice.

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