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  1. #1
    Joined
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    manila, philippines
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    Question how much power does a pc actually consumes?

    i've been wondering about this for ages...

    how much power does a pc actually consumes?
    just the CPU. no monitor included or other peripherals.

    using a 450watt power supply doesnt really mean i'm using 450watts of power right?
    i mean, if it does.. then thats a lot of power, especially with a pc running 24/7.

    just wondering.
    -madhaw

  2. #2
    Joined
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    Bedford, England
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    10,220

    Re: how much power does a pc actually consumes?

    Depends what PC. Mines using about 370-400watts on full load.
    Time to upgrade PSU me thinks.

  3. #3
    Joined
    Jun 2001
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    manila, philippines
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    117

    Re: how much power does a pc actually consumes?

    how did you know how much wattage your cpu consumes?

    my setup:

    athlon xp 1800+ @ 2.2ghz 13x169 1.6v
    asus a7v8x
    512mb ddr400
    asus 9600xt
    2 - 40gb seagate baracuda 7200rpm
    asus 52x48x52x cdrw
    enermax 350 watts psu
    1 - enermax 120mm fan
    2 - enermax 92mm fan
    1 - coolermaster 80mm LED fan
    coolermaster dual cold cathode
    volcano 11 HSF

  4. #4
    Joined
    Feb 2003
    Location
    Massachusetts - U.S.A.
    Posts
    2,004

    Re: how much power does a pc actually consumes?

    This guide will help you determine the requirements of your system components & if you search over at AMD they also have specs of their processors.

    http://www.firingsquad.com/guides/power_supply/

    Regards, Szandor
    Truth has always been in abundance. Its only due to the lack of its demand that we question its existence. - D. Bast

    Dance like no one is watching - Sing like no one is listening - Live each day as if it were your last. - Old Irish Saying

    H.S.T. - Happy Trails Dr. Gonzo!

  5. #5
    Joined
    Oct 2004
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    991

    Re: how much power does a pc actually consumes?

    In numerous PSU/case threads here I have posted a link to the AMD PSU Worksheet so people can make an informed decision on PSUs. The dated Firing Squad article is still a valid approach as they use the AMD Tech Doc method of calculating the power consumption for each item in a PC, which is exactly what you need to do. The power consumption is printed right on your drives, fans, etc. Video card power consumption is the biggest unknown -- like it's some friggin nuclear code or something and I am working to expose the power consumption on the latest X700/X800/6800 series video cards which draw a ton of power similar to a typical CPU.

    The AMD PC Builders Guide has the PSU worksheet and it's very simple to fill in the numbers and add them up. As the Firing Squad article shows, many PSUs simply do NOT have the proper current on all three PSU rails 3.3V, 5V & 12V. If even one rail is weak your PC will have problems. In addition the published PSU specs are the MAXIMUM power output per rail. You need to subtract the power used by the combined 3.3V and 5V rails from the total PSU wattage to see what is really left for the 12V rail because in most cases it's not the max. spec listed.

    http://www.amd.com/us-en/assets/cont...docs/31684.pdf

    See pages 26 & 27 of reference AMD tech Doc.

  6. #6
    Joined
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    manila, philippines
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    117

    Re: how much power does a pc actually consumes?

    now my head hurts too much info.
    so basically, if i have a 350watt psu, i doesnt really consume that much power right?

  7. #7
    Joined
    Oct 2004
    Posts
    991

    Re: how much power does a pc actually consumes?

    Wrong...

    The only way you know what your PC consumes is by doing the math, which ain't hard. Many PC components have the power consumption printed right on them. The Firing Squad page link below shows the 3.3V, 5V & 12V rails and the power each PC component uses. This should make it easy for you to add up what your PC uses based on what hardware you have. Then you check to see if the PSU you have or are considering can supply the proper current or watts on each rail and the total wattage your PC requires. You really don't want a PSU that has to operate at 100% all the time without any safety margin. It's always better to step up to a slightly higher PSU that supplies the correct rail current with a safety margin.

    http://www.firingsquad.com/guides/po...pply/page2.asp

  8. #8
    Joined
    Dec 2002
    Posts
    1,062

    Re: how much power does a pc actually consumes?

    According to the article, athlons and pentium 4's run entirely on the 12V rail, are Athlon XP's the same?

    The max load on a True430 is

    +5V +12V +3.3V
    36A 26A 28A

    If that is true, where in the tech documents is the 12V current displayed?

    So, let's see if I'm finding the right information on the other system parts, here's information from the Hitachi website on the IBM Deskstar 30GB

    Requirement +5 VDC (+/- 5%), +12 VDC (+10%/-8%)bb
    Dissipation
    Startup current (max. A) 2.0 (+12V) & 0.83A (+5V)
    Idle (W) 5.0 (1 disk)
    5.9 (2 disks)
    7.0 (3 disks)

    So the drive draws 2.0A from the 12V rail and 0.83A from the 5V rail? Is that what I was looking for?

    This is odd though, the WD600BB isn't on western digital's website....

    The CDRW and DVD-ROM drive information isn't on the official website, the power consumption that is...

    The CPU fan takes 0.76A from the 12V rail

    Where could I find the power consumption for the other hard drive, CDRW, DVD-ROM, and the motherboard?
    The case fans take 0.5A each from the 12V rail

    So the fans alone take 2.76A from the 12V rail

    The power consumption for the motherboard isn't listed on the motherboard's site(Abit) either...

    Where could I find the information for the other hard drive, CDRW, DVD-ROM, Abit NF7-S, and a GF FX 5950 Ultra?

    I searched through google and found this:

    http://www.xbitlabs.com/articles/vid...v-power_5.html

    Although, mine is a Gainward GF FX, does it use the same power as the MSI?

    This article shows the GF FX to use 4.92A on the 12V line, 2.29A on the 5V line, and 5.59A on the 3.3V line.

    That says it is on the lines in the AGP slot, do I just add that to the list of power consumptions in the firing squad guide?

    I guess it's time to go look at each drive for the power consumption on the physical drive itself.

    I know I'm spanning this across multiple threads, I'm just trying to figure out why my +5v voltage is between 4.78-4.84 while under load

    Edit: Got the HD voltage, the HD itself showed it as this:

    IBM HD: 5V - 300 mA 12V - 500 mA
    WD HD: 5V - 0.77A 12V 0.45A

    CDRW: 5V - 1.5A 12V 1.5A
    DVDROM: 5V 1.5A 12V 1.5A

    300 mA is .3A, right?

    So then so far if the video card information is right I have this:

    3.3V: 5.59A
    5V: 6.36
    12V: 11.63

    I still don't have these:

    CPU: Athlon XP 2500+ Barton - Where on the AMD site is it? I'm stupid
    Memory: 2x 512MB Corsair XMS PC3200
    Mouse: Microsoft Intellimouse Explorer(USB)
    Keyboard: Generic
    Motherboard: Abit NF7-S 2.0(Using onboard sound and NIC)

    It also said something about PSU fan, I'll have to check the antec site later tonight

    Some of the stuff I wasn't able to find, maybe I'm just blind
    Last edited by raz1337; 11-20-2004 at 06:12 PM.

  9. #9
    Joined
    Sep 2003
    Location
    Wichita, KS
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    34
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    1,370

    Re: how much power does a pc actually consumes?

    Your PC consumes as much power as it needs, a 350 watt power supply does not use all that power, it's only what it's capable of putting out.

    Most of the guides and calcs are way pessimistic. I have a wattmeter and tested my PC to see how much it actually uses, and it pulls 240 watts of AC power, so diving that into an 70% efficiency for the AC->DC conversion my system only uses around 170 watts for all of its components, and those components are:

    A7N8X-E Dlx mobo
    Athlon XP Barton 2800+ @ 3200+ speed
    Radeon 9800 Pro
    2x 512 MB PC3200 memoy
    2x 7200 RPM HD's
    3x CDRW/DVDRW drives

    Fairly typical type of system, and uses nowhere near the power most people think by using the calcs. My Antec True 430 is nowhere near stressed

  10. #10
    Joined
    Dec 2003
    Location
    NY
    Age
    26
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    3,523

    Re: how much power does a pc actually consumes?

    download the overclockulator, does all the work for you
    http://www.pimprig.com/downloads/ind...d%20Utilities&
    also has other useful things, enjoy
    Phenom 9850 Black Edition @ 3.2GHz | Biostar 790gx | Corsair XMS2 DDR2 800 4GB | Asus Radeon HD4870 512MB | Antec NeoHe 550 | Soyo 26" lcd

  11. #11
    Joined
    Oct 2004
    Posts
    991

    Re: how much power does a pc actually consumes?

    Raz1337 you're doing just fine. The AMD Tech Docs will show you the max CPU power consumption at the link below. From the Athlon on the AMD CPUs use the 12V rail for power, as do Pig 4s. Memory uses about 10W per module and its from the 5V rail so it's 2 amps per module, if run at stock voltage and speed. Once you start overclocking the power consumption can rise quickly. The Firing Squad link shows typical USB of .5 amps on the 5V rail and .25 amps. each for the mouse and keyboard on the 5V rail. The Mobo typically uses 3 amps on the 3.3V, 2 amps. on the 5V and .3 amps on the 12V rails per the Firing Squad article. They also list typical power consumption for modems and other hardware.

    See page 21 of this AMD Tech Doc which shows 68.3W max or 41.4 amps @ 1.65V for the XP2500+ when run at nominal voltage and frequency. That's roughly 5.7 amps from the 12V rail. Power consumption goes up with speed and voltage so if you are overclocking you need to account for this added load.

    http://www.amd.com/us-en/assets/cont...docs/26237.PDF


    TDG if you're using an inductive wattmeter you're probably not getting a real accurate reading. There is no magic to this power consumption calculation. The drives and fans all have the power consumption printed on them so when you add it up thats the real deal. Even if the ratings are 10-20% high, you always want a safety margin so the PSU isn't maxed out all the time. And it's not just total wattage that's at issue. It's the correct power available on all the rails, all the time. That's where the problem comes in when one rail can't supply the required current, yet the total current may be below the PSUs total wattage. Again to be clear we are looking at worse case scenario when everything is under full load. If your PC never sees much load then the only time you're likely to encounter problems are during cold boot when there is a max power draw on all hardware components. If on the other hand you do graphics intense work or play video games then you want to be certain you have enough power to handle the full load calculations, which many PSUs can't do.

  12. #12
    Joined
    Dec 2002
    Posts
    1,062

    Re: how much power does a pc actually consumes?

    So then how can I figure out what's causing the low +5v voltage? I'm guessing with it reaching as low as 4.78, is it even safe to set it at 3200+ speeds and 2-3-3-7 timings like I did with my 8RDA+? Or is that a question for the overclocking forum? :P

  13. #13
    Joined
    Oct 2004
    Posts
    991

    Re: how much power does a pc actually consumes?

    Technically the 4.78V reading is just within the ATX specs for 5V +/- 5%. In theory all **should** work fine at that voltage. I would expect the combined total wattage available on your True430 for the 3.3V and 5V rails exceeds your total wattage from your calculations??? Did you check to make sure that is true??? Once you know the total wattage consumed by the 3.3V and 5V rails you subtract this from the total PSU wattage available to determine what power is left for the 12V rail. All three rails must have sufficient current to meet the power consumption loads.

    The lower than desired, but still within spec 5V rail voltage may not be due to insufficient available power, it may be due to less than optimum voltage regulation by the PSU. In addition to having enough current available on a given rail, a quality PSU controls the voltage very tightly. +/- 5% is the maximum ATX spec. Some PSUs will keep the voltages within 3% and the very best PSUs hold the voltage within 1% of spec. A good PSU not only holds the voltage within spec, it minimizes voltage fluctuation with load. A rail that has a lot of voltage fluctuation can cause problems even when "in spec" on actual voltage. You want rock steady voltages if you're overclocking.

    I hope that the 4.78V reading you have, was taken at the ATX Mobo connector with an accurate digital volt meter, because software voltages and temps are usually quite inaccurate and can send you on a wild goose chase...

  14. #14
    Joined
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    Location
    NY
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    26
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    3,523

    Re: how much power does a pc actually consumes?

    yea, software unreliable. I tested my 5v from a molex and idle i was 5.01 and load I was 5.02, all with a antec 350 Software said my 5v was like 4.8
    Phenom 9850 Black Edition @ 3.2GHz | Biostar 790gx | Corsair XMS2 DDR2 800 4GB | Asus Radeon HD4870 512MB | Antec NeoHe 550 | Soyo 26" lcd

  15. #15
    Joined
    Jun 2001
    Location
    manila, philippines
    Posts
    117

    Re: how much power does a pc actually consumes?

    thanks guys for shedding some light to this.

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