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Determining Necessary Power Requirements for PCs?

Posted by Cliff on from the how-much-wattage-do-ya-need? dept.

kchayer asks: "If all goes well, I'm looking at purchasing some new hardware this summer to beef up my current system. However, despite some searching I've done on Google and elsewhere, I've been unable to determine an accurate answer for this question: How big of a power supply will I need? I am looking at an SMP (dual) Intel P-III 1ghz system, with three 80mm case fans, a high-end 7200 RPM IDE hard drive, a hard drive fan, high-end video card (possibly even Nvidia's new GeForce3), DVD, CD-RW, SBLive!, and other standard hardware. Is my current 300W ATX supply going to cut it? Or do I need something bigger? Suggestions as well as ways I can calculate potential power consumption would be appreciated."

10 comments

  1. What to do. by Night0wl · · Score: 1

    volts * amps = watts.

    So, if you're really bored track down the voltage and ampere rating for all the devices in your comp, add up there wattages, add a bit, and bingo...

    --
    Computational Madness in a round package.
    1. Re:What to do. by spunkmirej · · Score: 1

      Power supplies supply 12V, 5V and 3V power. It's the sum of the wattages available on these 3 lines that gets stamped on the PSU.

  2. Should be fine, and the way to check. by Christopher+Thomas · · Score: 5

    How big of a power supply will I need? I am looking at an SMP (dual) Intel P-III 1ghz system, with three 80mm case fans, a high-end 7200 RPM IDE hard drive, a hard drive fan, high-end video card (possibly even Nvidia's new GeForce3), DVD, CD-RW, SBLive!, and other standard hardware. Is my current 300W ATX supply going to cut it?

    It should.

    The Right Way to figure this out is to look up figures for *peak* power consumption for the CPUs and the graphics cards from the various hardware review sites (Ace's, Sharkey's, etc). Then add the power ratings on all of the fans (should be on the box if you're buying them as discrete components, and you can get the store to look it up if they're building it for you). Then multiply the whole shebang by 1.3-1.5x as a safety factor.

    Or, you can use the back-of-the-envelope method:

    - 50W each is about the right ballpark for the processors. Spec 100W for this.
    - If all of your fans together take more than 50W, I'll be very surprised. Spec 50W.
    - If your graphics card takes more than 50W, the PCI bus should start smouldering. Unless you have a Voodoo 5, spec 50W.
    - Hard drives and so forth aren't *horribly* power-hungry. You have a 100W margin left. You should be fine.

    Heck, you'd probably be fine with a 250W supply or lower, but you don't want to risk having your computer hang when you're using it most thoroughly.

    YMMV.

    1. Re:Should be fine, and the way to check. by Pogue+Mahone · · Score: 1

      > The Right Way to figure this out is to look up
      > figures for *peak* power consumption for the
      > CPUs [etc]...

      What you should really do if you want to be thorough is to add up the total worst case current that each component draws from each rail (+/-5v, +/-12v) and make sure that the PSU can adequately cope with all these demands. The max current on each rail should be in the PSU specs.

      However, 300W *should* be enough as long as you're not running a space heater from the PSU too (*cough* Pentium *cough*)

      --
      Every bloody emperor has his hand up history's skirt [Peter Hammill/VdGG]
  3. One company sizes online by scotpurl · · Score: 3

    PcPowerCooling.com has a few web pages to cycle through that does some power supply sizing. You pick what type of power supply, how big a case, how many CPUs, RAM, disks, and it suggests. And they sell some really good stuff.

    And while I'm on the topic of selector web pages, APCC.Com also has some interesting selectors. UPS, Cable, surge, and other things.

  4. My machine has a big plug by green+pizza · · Score: 2

    My deskside workstation has a NEMA 6-30 twist lock plug (30 amps @ 240v) but then, it is an old SGI Onyx.

  5. Yeah, well. by dave-fu · · Score: 1

    Geforces are notoriously power-hungry beasts. If you want your maddeningly hard-to-reproduce crashes, hangs, pops and bangs, go with a 250W power supply.
    They sell 400 watters these days and it's not a bad idea to snarg one. Just tell yourself you'll be able to carry it over to your next computer like you did with your 300 watter.

    --
    Easy does it!
    This comment has been submitted already, 276865 hours , 59 minutes ago. No need to try again.
    1. Re:Yeah, well. by Aphexian · · Score: 1

      Yeah,

      He said that when he got his 300 watter, and now you're suggesting a 400 watter.

      It's amazing how we can placate ourselves with a reason even when previous experience shows it to be a lie.
      :-) Hehehehe...

      -John.

  6. Overclocking for the rest of us... by wardomon · · Score: 2

    I've found that by unplugging my computer from the 120V outlet and connecting it to 240V, I obtain a brief but blazing increase in performance.

    --

    - - - If the sun is a star, why can't I see it at night?
    1. Re:Overclocking for the rest of us... by larien · · Score: 2
      "Blazing" being the operative word.

      Well, at least until you get the fire extinguisher...
      --