Joined: 11 Dec 2003 Posts: 4750 Location: Pennybridge, Sweden
Posted: Sun Nov 20, 2005 3:10 pm Post subject: The power supply
Even more info from the Encyclopedia:
Quote:
Supplies the system with power. Its purpose is to convert incoming AC (alternating current) into DC (direct current), in order to provide power to an entire PC.
ATX PSUs follow ATX Form Factor specifications, which also covers the entire PC. They can be found here.
A typical ATX PSU may have several different cables coming out of it (pin number is within the parenthesis):
# ATX12PWR1: A large rectangular 20-pin connector for your mainboard. Supplies power to the system.
# ATX12V: Some PSUs are also equipped with this 4-pin power connection that some mainboards require to work. Supplies extra voltage to the CPU and mainboard.
# 12VDC & 5VDC: 4-pin molex-connector that supplies power to peripheral hardware such as harddrives, CD/DVD-players and graphics cards. The four cables are: +12V (yellow), Earth (black), Earth (black) and +5V (Red). Floppy drive connector as well.
# AUXPOWER: Short for auxiliary power, which pretty much speaks for itself. Six cables: +5V, 2x 3.3V and 3x Earth. Not very common though and used even less.
# Serial ATA power connector: New harddrives with the SATA-interface require a special connection. A part of the 2.0 revision, but if you don't have these coming out of you PSU there are molex-converters to buy. (detailed requirements can be found here)
An ATX PSU's output lines must, as per ATX specifications, fall within 5% of nominal voltages, and have a ripple voltage of no more than 50 millivolts, peak-to-peak, on the +3.3 and +5 lines, and no more than 100 mv on the +12V supply line:
12V: min 11.4, max 12.6
5V: min 4.75, max 5.25
3.3V: min 3.14, max 3.47
Typical use:
12V: harddrives, Intel processors, FireWire, graphics cards, serial port, etc.
5V: harddrives, AMD processors, CD/DVD-players, floppy, memories, PCI and AGP-cards, USB, PS/2, parallel port, etc.
3.3V: AGP-slot, memories, northbridge & southbridge and other mainboard components, PCI-cards , etc.
(Some units occur twice but they do however use more than one voltage)
Joined: 11 Dec 2003 Posts: 4750 Location: Pennybridge, Sweden
Posted: Mon Jan 07, 2008 6:39 pm Post subject:
Winmmister wrote:
I have heard that a 1000watt PSU (it could be a hair dryer) is more economical than a 500W as an example. Is it real??? how???
Both yes and no.
It depends on how much power your computer consumes. The peak efficiency is namely in the middle range of the rated wattage, not the top.
E.g.
Your PC consumes 300W.
A 400W PSU with a 75% efficiency at 75% load (300/400) the PSU will drain 400W from the outlet.
Consumption / efficiency = power from the outlet.
A 500W power supply would have a 85% efficiency at 60% load (300/500), would only draw 350W from the outlet.
I hope that wasn't too confusing, or that I made a mistake somewhere.
It all comes down to the efficiency of the power supply, but a good modern power supply can keep a high efficiency even at 80% load, which makes all of the above not matter.
//Andreas _________________ "I'm sort of a postmodern vegetarian, I eat meat ironically" "You are our Swedish superhero "
Forget everything, knowledge is your enemy, it's only going to make you second-guess yourself."
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