Fundamentals - Building the Perfect PC - page 13

• The next step down in noise level is a power supply that is specifically
designed to minimize noise. These power supplies cost a bit more
than comparable noise-reduced power supplies but produce as little
as 18 dB at idle, and not much more under load. A system that uses
one of these power supplies (and other similarly quiet components)
can be nearly inaudible in a normal residential environment. You
won't have any trouble recognizing any of these models, because all
of them are advertised and promoted as “Quiet PC” or “Silent” models.

• Finally, some power supplies use huge passive heatsinks rather than
cooling fans. These power supplies, such as the FSP ZEN 400 ( http://
www.fspgroupusa.com ) , have no moving parts, and the only noise
they produce is a very slight buzz from the electronic components.

Choose an efficient power supply
Power supply efficiency has a direct bearing on system noise level. Every
power supply requires higher input power than the output power it pro-
vides, and that power difference is converted to heat within the power
supply. For example, if the system actually requires 200W from the power
supply, a 67% efficient power supply draws 300W of input power to pro-
vide that 200W of output power (200W/0.67 = 300W). That extra 100W is
converted to heat within the power supply. An 85% efficient power sup-
ply requires only about 235W of input power to provide 200W of output
power. The difference between 300W input and 235W input power trans-
lates to an extra 65W of heat within your system. The efficiency of main-
stream power supply models ranges from about 65% to 90% or higher.

The 80 PLUS Initiative
The 80 PLUS initiative sets standards
for power supply efficiency. A power
supply that meets the basic 80 PLUS
requirements must be at least 80%
efficient at 20%, 50%, and 100%
load, and must have a power factor
(PF) of at least 0.9 at 100% load.
The 80 PLUS Bronze certification
requires the power supply to be at
least 85% efficient at 50% load and
82% efficient at 20% and 100% load,
with a PF of 0.9 or better at all three
load levels. The 80 PLUS Silver and
Gold certifications require the power
supply to be at least 85%/88%/85%
efficient or 87%/90%/87% efficient,
respectively, again with a PF of at
least 0.9 at all three load levels.
Less than half of the power supplies
currently sold have any 80 PLUS
certification. Less than 4% have the
80 PLUS Gold certification, and about
the same percentage have the 80
Plus Silver certification. Roughly 20%
have the 80 PLUS Bronze certifica-
tion, and another 20% the basic 80
PLUS certification.

Choose a quiet CPU cooler
As processor speeds have increased over the last few years, manufactur-
ers have gone from using passive heatsinks to using heatsinks with slow,
quiet fans to using heatsinks with fast, loud fans. Current processors differ
greatly in power consumption from model to model. At the lower end of
the range—less than 50W—nearly any decent CPU cooler can do the job
with minimal noise, including the stock CPU coolers bundled with retail-
boxed processors and inexpensive third-party units. At the middle of the
range—50W to 90W—standard CPU coolers begin to produce intrusive
noise levels, although specialty quiet CPU coolers can cool a midrange
processor with little or no noise. At the upper end of the range, even the
quietest fan-based CPU coolers produce some noise. Here are some tips
to keep in mind when selecting a CPU cooler:

• For a processor with low to moderate power consumption, try using
the stock CPU cooler supplied with the retail-boxed processor. If it pro-
duces too much noise, install an inline resistor to reduce the voltage
supplied to the fan, which reduces fan speed and noise. Resistor kits
are sold by quiet-PC vendors such as FrozenCPU ( http://www.frozencpu.
com ), QuietPC USA ( http://www.quietpcusa.com ), and Endpcnoise.com
( http://www.endpcnoise.com ).