JUNE 2004 MAXIMUMPC 57

The foundation of a stable and long-lasting system is a high-

quality power supply. But choosing the right one is anything but a

straightforward process. We’re here to help by answering all your

PSU questions: how much power you really need, how to decipher

cryptic labels, and how to sort the good from the bad

Frenetic CPUs and flashy video-

cards dominate the headlines,

but the humble power supply unit

(PSU) has gone largely ignored. It’s

sad, but understandable. After all,

it’s an insipid little box that makes

for a poor conversation piece even

among geeks. The fact that even

the brawniest PSU won’t yield an

extra ounce of computing prowess

certainly doesn’t help.

Shamefully, some system ven-

dors slyly exploit consumers’

general lack of interest in and

understanding of PSUs by install-

ing cheap, barely adequate power

supplies in their systems. That’s

where we come in. We’re here to

set the record straight about the

most underrated PC component

of all time.

At a fundamental level, the PSU

is a collection of electrical compo-

nents that converts 120V AC power

from your wall socket into 12V, 5V,

and 3.3V power that your computer

uses. If you’ve got a crappy power

supply, the side effects may take

a while to manifest, but manifest

they will. They’ll appear in the form

of system crashes, spontaneous

reboots or shutdowns, and even

component damage over time.

Whether you’re buying a PC off the

rack, building one from scratch, or

simply upgrading, settle for nothing

less than a quality power sup-

ply—the PSU is not the place to

pinch pennies.

Sorting out the quality power

supplies from the junky ones

is no simple task. You can’t

even look inside the damn thing

(unless you want to risk electrical

shock—even if the power sup-

ply is unplugged). Don’t sweat it.

We’re going to show you what’s

inside the box, how to interpret the

strange glyphs on the label, and

how to know which PSU is right

for your rig.

—DWIGHT LOOI

HEATSINKS: Transistor switches and power

diodes in the PSU produce loads of heat. The

heatsink helps whisk away the heat from these

components, a vital task considering a power

supply becomes less efficient as its tempera-

ture rises.

The foundation of a stable and long-lasting system is a high-

OUTPUT CAPACITORS (beneath heat-

sink): Essential for system stability, these pro-

vide the PSU with the excess muscle needed

when the electrical demands of your PC’s com-

ponents suddenly changes, such as when two

optical drives spin up simultaneously.

POWER FACTOR CORRECTION

CIRCUIT (beneath PCB): Computers, like

many other electrical appliances, draw a lot

more power at the instant they’re turned on—

as much as four times the amount drawn under

regular use. While this spike in power demand

lasts just a fraction of a second, it may be

enough to trip a circuit breaker in a home or

office that’s running numerous electrical appli-

ances. The duty of the power factor correction

circuit is to smooth out this initial spike as much

as possible, reducing its amplitude and prevent-

ing circuit overloads.

Watts Up?

The Shocking Truth about Power Supplies