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What size power supply do I need for my CPU/motherboard combo?

By melkor849
Apr 9, 2012
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  1. Hi,
    I'm currently running a machine with an 8-core processor and a 550W Power Supply.

    The machine won't run on all 8 cores. It gets to the "Windows Startup" screen and shuts down. It's not running hot as far as I can tell, and if I manually shut down a pair of cores in the BIOS it runs just fine. I am currently running it on 6 cores, but would like to run it on all 8.

    Is my Power Supply not powerful enough, or do you think it's another problem?
    Thanks.

    My System:
    Processor: AMD FX 8120 (8-core), 3.1GHz Socket AM3+
    Motherboard: ASUS M5A88-V EVO
    Power Supply: Logisys 550W ATX12V
    Video Card: *Currently using onboard*
  2. Blkfx1

    Blkfx1 TS Addict Posts: 889   +171

    Your 550W PSU should run that system just fine. Is your BIOS up to date?
  3. Marnomancer

    Marnomancer TS Booster Posts: 808   +51

    As far as the PSU is concerned, you can check the manufacturer's website for product requirements. If your PSU and other components pass the requirements, it could be another problem.
  4. melkor849

    melkor849 TS Rookie Topic Starter

    I installed the most recent BIOS update as soon as I had the OS up-and-running. As far as I know it's still the most recent.

    I have contacted AMD about the problem, but they have yet to send me a reply.
  5. dmill89

    dmill89 TS Guru Posts: 737

    It would be except that isn't a 550w PSU. That Logysis is a severely overrated piece of junk. I'd be suppressed if that PSU actually outputs more than 300w. Any good 500w+ PSU should run that system just fine, even a 400-450w should be ok as long as you don't add a video card.

    Here are some recommendations:
    ENERMAX Tomahawk ETK500AWT =$70 ($60 after rebate)
    PC Power and Cooling Silencer MK III 500W Modular = $80 ($60 after rebate)
    ENERMAX NAXN 82+ ENP650AWT B 650W = $90 ($80 after rebate) this gives you some extra head room if you plan on adding a video card in the future
    PC Power and Cooling Silencer MK III 600W Modular = $90 ($70 after rebate) again extra head room for a video card
    Antec EarthWatts EA-650 GREEN 650W = $80 ($60 after promo code) again extra head room for a video card


    If you are on a tight budget this one is ok, (currently one of the best budget PSUs out there) but it is not as good as the others and won't leave you room for future upgrades:Antec VP-450 450W = $40
  6. melkor849

    melkor849 TS Rookie Topic Starter

    Thanks, dmill.

    I'll probably go ahead and get a new power-supply then. I'll post back when it gets here and let y'all know the results. :)

    BTW... Is there a program you can run that will detect the actual working wattage of the PSU?

    Thanks.
  7. Blkfx1

    Blkfx1 TS Addict Posts: 889   +171

    I didn't even notice then name. Yeah.. I would agree with Dmill89 then. Let us know how it goes after the PSU change.
  8. melkor849

    melkor849 TS Rookie Topic Starter

    Will do.

    I'll probably go for the Antec 650W. I may be adding a GFX Card in future.

    Thanks, again.
  9. dmill89

    dmill89 TS Guru Posts: 737



    There are many calculators to find system draw. This is the one I usually use: extreme.outervision.com/psucalculator.jsp, Put in your hardware, set everything to 100% draw then take the number it gives and add 15% for head room.

    As for the PSU itself the only real way to test its maximum output is to load test it until it either the overload protection shuts it down (good PSUs do this) or it explodes (bad PSUs usually do this). Opening it up and looking up the data sheets / specs. for the bridge rectifier, primary switchers, output rectifiers, and transformers can also give you an idea of its capacity (Warning PSUs contain high voltages, do not open unless it is unplugged and you are sure the primary capacitors are drained), however this may be beyond the level of the average user.
  10. melkor849

    melkor849 TS Rookie Topic Starter

    Hmm... ok

    My computer would shut down when I tried to run it on all 8-cores, I guess that was the problem.

    Thanks.
  11. melkor849

    melkor849 TS Rookie Topic Starter

    It worked!

    I purchased the Antec 650W Power Supply, and after everything was installed I re-activated all the cores. Everything is running smooth and faster than ever. ;)

    Thanks again for all your help.
     
  12. dmill89

    dmill89 TS Guru Posts: 737

    Glad to hear everything worked out.

    The Powersupply is not the place to cut corners, but is often the most overlooked component. Too many people don't realize that this is one of the most important components in the system since it provides the power for everything else to work. At best a week / poor quality power supply leads to the kinds of instability and performance problems you experienced, at works it can lead to severe component damage.

    Just be glad you caught the problem before anything really bad happened.


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