MaximumPC 2004 06

12V are entirely different. Some EPS 12V

PSUs also offer an additional 6-pin SSI

connector for use by mobos with an AGP

Pro110 slot.

In the upcoming years, the ATX form-

factor will be gradually supplanted by

the BTX formfactor. BTX, or Balanced

Technology eXtended, specifies compo-

nent placement in a three dimensional

space rather than a two dimensional

space, and pays special attention to heat

management and airflow. With this in

mind, the CPU will be moved to the front

of the case, closer to the intake fan, and

the expansion slots will change sides.

We’ll probably start seeing viable

BTX motherboards carrying Intel’s new

LGA775 CPU socket sometime this year.

The rise of BTX may eventually bring an

end to ATX’s decade-long reign, but as

of today, BTX is barely peeking over the

horizon. It’s not yet clear whether ATX

power supplies will be compatible with

this new spec.

How important is a warranty

for a power supply?

To be honest, most of us can’t live a day

without our PCs. It would be unbearable

to be “unplugged” for a week or more

while waiting for a warranty repair/

replacement to make its way through

the postal system. Having said that, a

good warranty isn’t just a ticket to a

replacement unit should the PSU fail,

it’s also an indication of the confidence

a manufacturer has in its product. With

established brands, a long warranty can

be as much a testament to the product’s

quality as it is a promise to service it.

How long should a quality

power supply last? What are

the early signs of PSU failure?

A good PSU should render years of

trouble-free service. Most well-built units

will last a good three to five years, and

will likely still be in good health even

after your system has become obsolete.

But with this said, if you’re overhauling

your system, you should probably think

about a new power supply. You don’t

want your new PC to be eventually poi-

soned by an aged, failing PSU.

Typically, the first indication of trou-

ble is abnormal sounds coming from

the cooling fan. This is usually a pre-

cursor to the fan completely giving up

the ghost, and it’s frequently possible

to replace the fan before that happens.

Most PSUs use 80mm fans and they

should be replaced at the first indica-

tion of anomalous operation or unchar-

acteristic sounds.

A fading PSU may create all manner

of crashes, random shutdowns, and

intermittent refusal to power up. This

is often the result of the output voltage

falling out of specification. However, all

too often, the first indication you’ll get

from a failed power supply is a burning

smell and a whiff of smoke, followed by

a blank screen and an eerie silence.

We can’t say it strongly enough: If

you suspect that your PSU is ailing,

deal with it now, or face much more

severe consequences in the future.

What is Advanced Power Man-

agement and ACPI? Is my power

supply compatible with them?

Advanced Power Management, or APM, is

a standard co-developed by Microsoft and

Intel that allows a system to be in one of

six different states pertaining to power use:

On, APM Off, APM Active, APM Standby,

APM Suspend, and Off. This is meant to

provide users with a way to conserve

power via BIOS-directed power manage-

ment. While this may sound like an addi-

tional PSU function, it isn’t.

The only thing APM requires of a

power supply is the ability to turn power

on/off via an electrical signal and the

presence of a standby voltage. All ATX

power supplies are required to have

these features. However, for APM to func-

tion properly, the operating system, BIOS,

mobo, and other peripherals need to be

APM-compliant. If some components are

not APM-compliant, you may get errors

or freezes when your system goes into

standby mode or hibernates.

ACPI, or Advanced Control and Power

Interface, is a newer and more capable

power management scheme developed

by Compaq, Intel, Microsoft, Phoenix, and

Toshiba. Unlike APM, this standard is OS-

directed rather than BIOS controlled. All

ATX power supplies are ACPI-compatible,

so no worries here either.

POWER SUPPLIES

60 MAXIMUMPC JUNE 2004

ATX 12V POWER CONNECTOR

USED FOR: Additional CPU power

Conjunction Junction

ATX MAIN POWER CONNECTOR

USED FOR: main motherboard power

PERIPHERAL (MOLEX) POWER

CONNECTOR

USED FOR: Hard drives, optical drives,

some PCI and AGP cards

FLOPPY POWER CONNECTOR

USED FOR: Floppy drives, some PCI and

AGP cards, fans

SERIAL ATA POWER CONNECTOR

USED FOR: Serial ATA peripherals (hard

drives and optical drives)

There are five main connectors

you’ll find on the latest power

supplies. Here’s a power

connector peepshow to help

you identify them.