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  1. #1

    Default What size PSU for new PC?

    Hi,

    I've compiled a list of components that I want to buy to build a new PC. I'm wondering what size PSU would supply sufficient power for the PC. I've used an online PSU calculator but would also like to get some real-world data from people who might have a similar PC build. FYI, I will not be doing any overclocking of components and will use whatever stock cooling comes with the case and CPU & video card.

    Asustek P5B-E Plus
    Intel Core 2 Duo E6600 2.4GHz LGA775
    Corsair DDR2-800 memory module x 2
    Seagate SATA hard drive 7200rpm x 2
    Asustek 8800GTS 320MB PCI-E
    Creative SB Audigy 2
    LiteOn SOHW-1635S 16X Dual layer


    The PSU calculator came up with a value of about 480W, so would a 500W PSU suffice for this PC build?

  2. #2
    Unknown Device wratterus's Avatar
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    Default Re: What size PSU for new PC?

    I would say 500w minimum... more like a 550 or 600 for that system.

    Never skimp on a PSU. and get a good brand, make sure each 12v rail has enough amperage and stuff on it.. often the cheaper psus don't have a very high amp rating. i would recommend this psu for your requirements.

    i'm not saying it's the only one that would work...there are hundreds out there that will work for what you need. I have had very good expreiences with the toughpower PSUs in the past

    Good luck!
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    Senior Member Strommer's Avatar
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    Default Re: What size PSU for new PC?

    xmojo1, you may want to consider a psu that is quiet. Maybe this would not be a concern for you but the hum/buzz that mine makes is annoying. Some are advertised as being quiet. BTW, 500w minimum sounds good but also think of what you may add later on - you don't want to be cut short if in a year or two you upgrade a video card or psu that needs more juice.
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    Senior Member pctek's Avatar
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    Default Re: What size PSU for new PC?

    Quote Originally Posted by xmojo1 View Post

    The PSU calculator came up with a value of about 480W, so would a 500W PSU suffice for this PC build?
    It was probably exaggerating. Have a read of this:
    http://www.silentpcreview.com/article28-page3.html

    500w is fine.
    I'd just make sure it has 37a on the 12v and is a reputable brand such as Enermax..

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    Default Re: What size PSU for new PC?

    I have an Ennermax 701 600 watt. 600 would be a minimum I would go for in any new machine. Since newer video cards really like the extra juice.

    If you want extremely quiet get a Seasonic!

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    Default Re: What size PSU for new PC?

    Quote Originally Posted by pctek
    500w is fine.
    I'd just make sure it has 37a on the 12v and is a reputable brand such as Enermax..
    37A on the 12V supply, leaving only 56W total for the 5V and 3.3V rails?

    I'd like to see where the 37A goes. I'd guess 1.2A for the DVD, 2A max for the HDD. If the (1.6, 2.2 ?) CPU supply is generated from this it does not (e.g.) use 30 A at 12V to supply 30A at the lower voltage. The switchmode voltage reducing module uses watts at the input to produce watts at the output. So if the output voltage (2.4 for easy artithmetic) is reduced by a factor of 5, the input current is less by nearly the same ratio. If the CPU pulls 30A, the voltage reducer will pull about 5A. Does the video card really pull nearly 30A at 12V? Those fans must be bigger than I thought.

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    Network Engineer SolMiester's Avatar
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    Default Re: What size PSU for new PC?

    Not many psu have 37a on the 12+v rail, I didnt think the GTS used that much power, maybe 26a, but not 37a. An ATI card yes!, but not Nvidia.

    I agreed with the quiet requirement though, my silverstone 650w zeus is a bit noisy.
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    Senior Member george12's Avatar
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    Default Re: What size PSU for new PC?

    Quote Originally Posted by Graham L View Post
    37A on the 12V supply, leaving only 56W total for the 5V and 3.3V rails?

    I'd like to see where the 37A goes. I'd guess 1.2A for the DVD, 2A max for the HDD. If the (1.6, 2.2 ?) CPU supply is generated from this it does not (e.g.) use 30 A at 12V to supply 30A at the lower voltage. The switchmode voltage reducing module uses watts at the input to produce watts at the output. So if the output voltage (2.4 for easy artithmetic) is reduced by a factor of 5, the input current is less by nearly the same ratio. If the CPU pulls 30A, the voltage reducer will pull about 5A. Does the video card really pull nearly 30A at 12V? Those fans must be bigger than I thought.
    I'd agree that 37A is more than enough. For that system, plus plenty of room for upgrades, I would say that any decent brand 500W PSU will do the job. Current gets complicated when power supplies have two or three +12V rails.

    I find the best thing to go on is the +12V combined maximum output (in watts). If it has one rail this should be the current times 12, in which case 30A should be plenty (360W at 12V). This is easily found in a good 450W PSU, where a cheap 500-550W might not. If it has more than 1 12V rail, it should say the combined wattage, and you want it to be more than 360W IMO.

    That CPU draws 65W - I don't know how efficient the power circuitry is but it wouldn't be more than 100W (8A) at 12V. The video card should draw about 120W, another 10A.

    All up, the draw on the 12V rail(s) should be well under 25A at maximum load, leaving plenty of room for upgrades.

    So don't go buy a 600W monster with 40A, unless you really want it.
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    Default Re: What size PSU for new PC?

    Quote Originally Posted by Google
    The quoted power requirement to run the 8800GTS is 26a on the 12v rail. That 26a is for the ENTIRE system, not for just the card...
    That's the extract given for a link to another
    forum It seems that some confusion does exist. But "more is better" isn't the most economical policy.

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    Senior Member pctek's Avatar
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    Default Re: What size PSU for new PC?

    This is what I am referring to:

    +12V1@20A,+12V2@17A

    http://buyraidmax.com/product.php?pid=142

    or

    http://www.enermax.com.tw/english/pr...ay1.asp?PrID=5

    +12V1 0.5A/22A /+12V2 0.5A/22A


    As for what a GTS draws or not, whats wrong with getting a PSU that will last a few years? Instead of worrying about it all over again when the next graphics upgrade comes along.

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