How to size Power Supply for HTPC?

Discussion in 'Archived Threads 2001-2004' started by Steve Schaps, Feb 9, 2003.

  1. Steve Schaps

    Steve Schaps Auditioning

    Oct 30, 2001
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    I think that some of the problems I have are to do with the power supply in my Mini ATX case. It has a 200watt supply in it.

    Is there a way of working out how much power you need to run everything?

    I have a P4 1.5Ghz
    Asus P4S333 VM (only 3 PCI slots and 1 AGP)
    Leadtek 6X sound card
    ATI 9000 Pro Video card
    ATI 7000 PCI Video Card
    Pioneer 116 DVD drive
    512Mb DDR
    Seagate 40Gb HD
    Seagate 120Gb HD

    Will be installing the Holo3D at some stage as well.

    I am thinking of Changing the case to a Mini tower style but the Wife likes the Small case, desktop style which fits into the rack nicer (her words)

    Appreciate the Help
  2. Tekara

    Tekara Supporting Actor

    Jan 8, 2003
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    there's no real way of being able to tell how much power you need as everything in a computer uses more power when it's use and things like the hardrive can really spike in power usage. I've just been taking a conservative stance and recommending a 400w power supply to those that ask. with 400w your pretty safe from having anypower related problems and there's room for upgradeing or at least keeping it around for the future.
  3. Scott L

    Scott L Producer

    Feb 29, 2000
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    I think a quality Fortron/Sparkle 300 watt power supply is all you'd need. Something that has around 185+ watts on the combined 3.3 & 5v rails would be ideal. The one I recommended has 200. About $27 at Newegg and Directron.
  4. AndrewDSmith

    AndrewDSmith Auditioning

    Jan 2, 2003
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    Actually, there is an exact way to tell how much power you will use, if you have the knowledge to do so. What your looking at , in the extreme situation, would be 270W max power, based on your listed components.

    The problem is that I will assume that you forgot to list some items, most likey the fans, but also maybe NIC/modem, even if onboard (but only if used), floppy drive, or card reader. Even assuming that you don't have any of these, although I would assume you have some fans, the other concern isn't just total watts. It also depends on which rail the power is supplied from.

    Different devices are using the different rails for power, +3.3v, +5v, +12v and some use +3.3v and +5v or +5v and +12v. So, you need to calculate the total combined draw on each rail to make sure that it doesn't exceed the PSU's capabilities.

    It would seem that your +12v rail will see loads of up to 79W of draw. The +3.3v rail will see a draw of 86W. The +5v rail will see a draw of 40W. The 3.3v and 5v rail will be about 25W. The +5v and +12v combined draw will be up to 65W. So, when you combine the +3.3v draw and the 5v draw, you will see a max draw of about 126W, which I assume is where you're getting into trouble. Check the combined Max for the +3.3v and +5v rail on your PSU label(most likely about 110W). This is usually the major problem when it comes to PSUs, the combined rail.

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