Hardware Reference
In-Depth Information
Having a power supply with active PFC might or might not lower your electric bill (it de-
pends on how your power is measured), but it definitely reduces the load on the building
wiring. With PFC, all the power going into the supply is converted into actual work, and
the wiring is less overworked. For example, if you ran a number of computers on a single
breaker-controlled circuit and found that you were blowing the breaker periodically, you
couldswitchtosystemswithactivePFCpowersuppliesandreducetheloadonthewiring
by up to 40%, meaning you would be less likely to blow the breaker.
The International Electrotechnical Commission (IEC) has released standards dealing with
the low-frequency public supply system. The initial standards were 555.2 (Harmonics)
and 555.3 (Flicker), but they have since been refined and are now available as IEC
1000-3-2 and IEC 1000-3-3, respectively. As governed by the EMC directive, most elec-
trical devices sold within the member countries of the EU must meet the IEC standards.
The IEC1000-3-2/3 standards became mandatory in 1997 and 1998.
Evenifyoudon'tliveinacountrywherePFCisrequired,Ihighlyrecommend specifying
PC power supplies with active PFC. The 80 PLUS certification for highly efficient power
supplies also includes a requirement that the power supply has active PFC. The main be-
nefitsofPFCsuppliesisthattheydonotoverheatbuildingwiringordistorttheACsource
waveform, which causes less interference on the line for other devices.
SLI-Ready and CrossfireX Certifications
Both NVIDIA and AMD have certification programs that test and certify power supplies
to be able to power systems with multiple graphics cards in either a Scalable Link Inter-
face (SLI) or CrossFire configuration. This type of configuration puts extreme demands
on the PSU, because it not only has to power what would normally be a high-end mother-
board,CPU,andmultipledrivesinaRAIDconfiguration,butalsouptothreevideocards,
which may be capable of drawing 300 watts or more each.
The certification process involves PSU manufacturers sending PSUs in for testing,
whereby they are verified to supply sufficient power (and the proper type and number of
connectors) to run the desired graphics hardware as well as the system. Power supplies
thathavepassedeitherofthesecertificationsarevirtuallyguaranteedtoproducehighout-
put and use high-quality design, engineering, and manufacturing. For more information
on these certifications, as well as lists of certified PSUs, visit the following links.
•
Certified SLI-Ready Power Supplies
—
www.slizone.com/object/slizone_build_psu
•
CrossFire Certified Power Supplies
—
http://support.amd.com/us/certified/power-
