EXTREME Overclocking  - Powering Your PC: Truths and Misconceptions Article - Page: 11
Home | Reviews | EOC Forums | File Downloads | RealTime Pricing Engine | Free Magazines | Folding Stats Contact Us

Powering Your PC: Truths and Misconceptions
A Guide To Power Supplies

Date Published: May 18, 2005
Author: Jason Rabel


Power Supply Efficiency:

A power supply's efficiency rating is determined by the ratio of AC power going in to the DC power going out. Generally this comparison is done using Watts as a common unit of measurement. Anything less than 100% efficiency is dissipated wastefully as heat. In reality no power supply will be 100% efficient, that's just a fact of life, however you can (and should) avoid power supplies with very low efficiency ratings.

If a power supply is consuming 450 Watts from the AC side, but on the DC side the output is only 400 Watts, then the math tells us that the PSU is ~89% efficient in its power conversion and the other 11% (50W) is lost as heat. That 50W of heat is no different than if you were running a 50W light bulb, you pay for that power usage on your electric bill. Not to mention the heat must be cooled, so there is an additional cooling cost that some people don't think about. So in the short-term a cheaper PSU may fit your budget better, but in the long term you will end up paying for it several times over. It is definitely worth comparing power supply efficiency ratings and choosing the most efficient power supply that your budget allows for.

Below is a table from the ATX 12V v2.01 specifications5 stating the required & recommended minimum efficiency levels for PC power supplies (to be compliant with the spec).

Most modern quality power supplies seem to be floating around ~75% efficiency under a typical load, with some reaching as high as ~85% for enhanced silent operation. The greater the efficiency, the less heat generated, the less cooling required, and thus the capability for a quieter PSU.


Operating Conditions:

Power supplies are meant to operate under a variety of environmental conditions that aren't always the most optimum. Most PC enthusiasts tend to go overboard in the chassis cooling department, however some OEM designs, typical servers, and even extreme environments can restrict a PC to operate in the upper environmental range of its allowable specifications.

Heat is a power supply's worst enemy, every component in a power supply is designed to work most optimum at a specific temperature, but not necessarily a realistic operating temperature (especially under heavy loading conditions). Capacity diminishes as temperature increases, and eventually the part will fail if it exceeds design parameters. Many people do not think about this, depending on the average ambient temperature inside their PC chassis, the PSU may or may not be able to operate at its full capacity (depending on how well the PSU was designed).

According to the ATX 12V v2.01 specifications, a power supply should be able to operate and maintain running at full load in 50 C (122 F) ambient conditions. There are many power supplies that often overlook this specification, and will overheat and shutdown under a full load condition before reaching anywhere close to a 50 C ambient temp. I have seen one power supply that rated its specifications under 25 C (77 F) ambient conditions, which to say the least did not hold up well when the temperature increased. The only solution would be to reduce the ambient temperature, reduce the load, or get a better power supply.


Latest Reviews
Most Downloaded Files
Recently Added Files
Compare Prices On Top Brands!

Intel Processors
Core i7 - Haswell
i7-4770K  i7-4771  i7-4790  i7-4770  i7-4790S  i7-4770S

Core i5 - Haswell
i5-4670K  i5-4690  i5-4690S  i5-4590S  i5-4570  i5-4460  i5-4590  i5-4440S  i5-4430  i5-4440

Core i3 - Haswell
i3-4340  i3-4370  i3-4350  i3-4360  i3-4330  i3-4130T  i3-4160  i3-4130  i3-4150

AMD Processors
Vishera 8-Core AM3+
FX-9590  FX-9370  FX-8370  FX-8370E  FX-8350  FX-8320  FX-8320E

Vishera 6-Core AM3+
FX-6350  FX-6300

Kaveri 4-Core FM2+
A10-7850K  A10-7800  A10-7700K  A8-7600

Video Cards
nVidia GeForce GTX 900 Series
GTX 980  GTX 970  GTX 960

nVidia GeForce GTX 700 Series
GTX 780  GTX 760  GTX 750

AMD Radeon R9 Series
290X  290  285  280X  280  270X  270

AMD Radeon R7 Series
265  260X  250X  250  240

Search By Brand
ASUS  Diamond  eVGA  Gigabyte  MSI  PowerColor  PNY  Sapphire  Visiontek  XFX  Zotac

PC Memory

ASUS  ASRock  Biostar  ECS  eVGA  Foxconn  Gigabyte  Intel  MSI  Shuttle  Supermicro  Tyan 

Hard Drives & SSDs
Corsair  Crucial  Fujitsu  HGST  Intel  OCZ  Samsung  Sandisk  Seagate  Western Digital

  Technology Magazines FREE to Qualified Professionals.
eWeek MagazineeWeek is the essential technology information source for builders of e-business. Focuses on e-commerce, communications and Internet-based architecture. Oracle MagazineOracle Magazine contains technology-strategy articles, sample code, tips, Oracle and partner news, how-to articles for developers and DBAs, and more. Dr. Dobb's JournalDr. Dobb's Journal enables programmers to write the most efficient and sophisticated programs and help in daily programming quandaries. InformationWeekInformationWeek is the only newsweekly you'll need to stay on top of the latest developments in information technology.
  Other Popular Titles: PC Magazine, BusinessWeek, Baseline, Business Solutions, Software Magazine, InfoStor, Security Source , TelevisionWeek, more...
Copyright 2000-2015 EXTREME Overclocking. All rights reserved.
Disclaimer of Liability - Privacy Policy