Considering the Importance of the Power Supply

The power supply is not only one of the most important parts in a PC, but it is unfortunately also the most overlooked. The power supply, in the words of the late Rodney Dangerfield, gets no respect! People spend hours discussing their processor speeds, memory capacity, disk storage capacity and speed, video adapter performance, monitor size, and so forth but rarely even mention or consider their power supply. When a system is put together to meet the lowest possible price point, what component do you think the manufacturer skimps on? Yes, the power supply. To most people, the power supply is a rather nondescript, unglamorous metal box that sits inside their systems, something to which they pay virtually no attention at all. The few who do pay any mind seem concerned only with how many watts of power it is rated to put out (even though no practical way exists to verify those ratings), without regard to whether the power being produced is clean and stable or whether it is full of noise, spikes, and surges.

I have always placed great emphasis on selecting a power supply for my systems. I consider the power supply the core of the system and am willing to spend more to get a better unit. The power supply function is critical because it supplies electrical power to every other component in the system. In my experience, the power supply is also one of the most failure-prone components in any computer system. I have replaced more power supplies in PCs than any other part. This is especially due to the fact that, to keep system prices down, system builders are encouraged to use the cheapest power supplies they can find. A malfunctioning power supply can not only cause other components in the system to malfunction, but also can damage the other components in your computer by delivering an improper or erratic voltage. Because of its importance to proper and reliable system operation, you should understand both the function and limitations of a power supply, as well as its potential problems and their solutions.

This chapter covers the power supply in detail. I focus on the electrical functions of the supply and the mechanical form factors and physical designs that have been used in PC systems in the past, as well as today. Because the physical shape (form factor) of the power supply relates to the case, some of this information also relates to the type of chassis or case you have.

Recently the industry-standard ATX power supply used in PCs has been evolving, with new connectors appearing on newer power supplies as well as motherboards and video cards. There are adapters to convert the new power connectors to the old ones (and vice versa). However, in virtually all cases these adapters aren't necessary because, by virtue of their design, several of the old and new connectors are actually compatible. For those who are either building new systems from scratch or upgrading and repairing existing systems, knowledge of the new connectors and how you can almost always build, upgrade, or repair a system without purchasing unnecessary adapters will be invaluable. This chapter examines the evolutionary changes to the ATX power supply connectors and highlights the new connectors designed for the latest systems.