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Thread: Power Supply Sizing

  1. #1
    Junior Member
    Join Date
    Apr 2003

    Power Supply Sizing

    I just freaked myself out by reading an article on power supply sizing and have a question.

    I was told the Athlon or Pentium run on the 12V rail and that they pull between 7 and 9 amps. I added that to my HD's two 7200 RPM WD 120 Special edition and two IBM 15,000 RPM SCSI. They are all on all the time. I added a DVD and a DVD-R drive, fans and etc. and came up with the astonishing result that my system needs about 238 watts on the 12 volt rail just to turn on and function.

    Now 238 watts divided by 12 volts equals 19.833 Amps on my 12 volt rail.

    The reason for wigging out is because I am and have been running a Herolchi 475 watt PSU for about six months and it has been stable. On the side of the PSU it says it is rated for 15 Amps on the 12 volt rail.

    I know mathmatically that I am pulling at least 19 Amps continuously from this PSU on the 12v rail.

    So my question is: Am I in danger of burning out any minute? Is the total wattage of the PSU cumulative or what? I am not panicing because there haven't been any problems. But I like to be proactive when it comes to my beloved computer.

    Just so I don't have to type it latter I am running:

    Athlon XP 2800+ Barton
    Asus A7N8X Rev 2.0
    SATA RAID Dual Special edition WD HD's
    Adaptec 2100S (128MB on board) SCSI Raid with IBM 15000 RPM HD's
    ATI 9700 Pro
    1024MB Corsair 3500 Dimms 22251T 4bank
    16X DVD-ROM
    Liteon 32X CD Burner
    Pioneer A05 DVD Burner
    Either it's dark in here or the frame rate is so low I can't see.

  2. #2
    Super Moderator Super Moderator Big Booger's Avatar
    Join Date
    Apr 2002
    Without doing the math,
    I can tell you from experience, the more you have the better. Sincerely, consider upgrading it at some point, especially if you have a lot of peripherals connected to that machine, and if you plan to add any other hardware.

    I burnt a 350 watt about 4 months ago, running 3 HDDs, CDRW, DVD, Geforce 4 Ti4200, SB Live 5.1 Platinum, Promise Ultra 133 Raid, 2 NIcs, etc...

    I too hadn't had a problem.. then all of a sudden, I was typing in a website address, and I heared a noise like a squirrel's balls being bashed by a hammer..

    Turned out the PS took a crap on me.. smoke was everywhere, plastic pieces got all inside my case.. I had a time..

    But I think you should be free and clear with 475watts. If you are worried about it, use one of the free asus tools to check the amperage, voltage etc...

    or one of the motherboard monitoring softwares.

    I have an intel board and I use the Intel Active Alert, works well. Lots of info provided by that handy tool.

  3. #3
    Head Honcho Administrator Reverend's Avatar
    Join Date
    Apr 2002
    You'll find most PSU's carry a Max 15A Rating.
    Unless you have every peripheral in your PC running at full speed and under heavy load,you will never hit above the 15A.
    Even if you did overload the system,Herolchi PSU's have a thermal cut-out,which would kick in before you go over the max 15A rating.

    475 watts is plenty powerful enough.

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