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Thread: Testing stability on my psu

  1. #1
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    Default Testing stability on my psu

    Was having a few issues with my video card overclock and was wondering if it could be because my psu can't keep up with it.

    Let me know if I'm wrong.

    I have a year and a half old PC power&cooling silencer 750 crossfire edition

    My rig:
    i7 930 overclocked to 4.24ghz
    2 raptors in raid 0
    2 large 7200 hdds
    3 sticks of ddr3
    gigabyte ga-x58a-ud5
    Sapphire HD5850 1gb gddr5
    Swiftech dual fan watercooling setup
    2 dvd drives
    6 case fans

    I ran some PSU configuration program somewhere and it said i required 780w.. but I figured they were just trying to sell me a PSU.

    Anyway.. I have been getting BSOD's when I overclock my video card and some stuttering in game.
    I took my FLUKE TrueRMS 76 multimeter, grabbed a 4 pin square shaped 12v connector while my computer was on and it read 12.13v.

    Then I fired up my benchmark program (linX) and ran it. the voltage dropped to 12.12v underfull load. The same thing occurred when I fired up Black OPs.

    In my mind this is a very stable PSU and probably not my cause of issues?

    Am I correct to assume if this connector reads 12.12v that the rest of the 12v leads should read 12.12 since it's a single rail? (supposedly)
    Last edited by NGL_BrSH; 01-05-2011 at 02:42 PM.

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    Default

    Then stop overclocking your video card.
    Your system requires somewhere around 350W and the PSU is a very good one.

    Those websites are only informative and it doesn't say you need 780W, it recommends a 780W PSU.

    Are you using the latest drivers for the video card?
    Sent from my PC using my browser.

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    Default

    Let's calculate the max draw on this by hand, shall we...
    I'll cleverly copy-paste your list

    First off, CPU power draw is proportional to both voltage applied and it's operating frequency. The TDP for the 930 is the same as the one for the 975, so they're under the same envelope. This means that we'll take that a LGA 1366 CPU at 1.375V and 3.33 GHz draws exactly 130W fully loaded (as per TDP). Thus, at stock, the 930 should draw ~96W at full load.
    When OC'd to 4.24 GHz (and I'll assume 1.4V at least, maybe it's even more)
    that would yield around 198W at full load on all cores and threads. So...

    i7 930 overclocked to 4.24ghz - ~200W max
    2 raptors in raid 0 - ~50W max both together
    2 large 7200 hdds - ~30W max both together
    3 sticks of ddr3 - ~60W max all 3, scaled linearly with frequency, quadratic with voltage, if OC'd
    gigabyte ga-x58a-ud5 - ~80W max, including NIC, Sound, USB, etc.
    Sapphire HD5850 1gb gddr5 - ~160W max (stock, 725 MHz, around 1.05V)
    Swiftech dual fan watercooling setup - no idea, probably around 5W max for pump, 4-10W fans.
    2 dvd drives - ~10W together idle, ~60W both burning discs.
    6 case fans - ~2-10W per fan, closer to ~7, so 12-60W, probably ~40W sustained.

    Bottom line: 715W absolute max when everything is 100% utilized. This never happens, unless you run furmark + prime95 or wprime + atto disk suite on all hdds + burning 2 dvds + playing 7.1 TrueDTS music + transferring 1080p .mkvs over the network. You can safely assume 3/4 duty cycle when heavy gaming (it can only be lower, not higher), so around 530W max real-life. The power draw of the 5850 would rise to about 260W when pushed to 900 MHz at 1.2V, this would overload the PSU but not drown it, when at 100% duty cycle (see above, furmark etc.). I don't think your PSU is the culprit for the BSODs here. Either way, try loosening the OC on the CPU then OC the VGA to see if there's any improvement. I calculated total draw, maybe just the 12V rail is overloading...
    Careful what you wish for... You just might get it.

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    Default

    Thanks for a great response.

    I feel better now. I'll start overclocking the video card in a different fashion. ie voltage adjustment etc.

    Also the last question is about how to test 12v.. if i get 12.12v on one connector can i assume it's not dipping on the other 12v connectors?

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    Default

    Quote Originally Posted by NGL_BrSH View Post
    Thanks for a great response.

    I feel better now. I'll start overclocking the video card in a different fashion. ie voltage adjustment etc.

    Also the last question is about how to test 12v.. if i get 12.12v on one connector can i assume it's not dipping on the other 12v connectors?
    You can't, and it most likely is dipping from all the current running through them. But don't worry, it takes craploads of amps flowing to make any significant v-drop.
    Careful what you wish for... You just might get it.

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    Default

    ok.. well i'm at 825mhz on the core clock. So you're saying I'm good. I'll take that and move on.

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    Default

    Quote Originally Posted by NGL_BrSH View Post
    Anyway.. I have been getting BSOD's when I overclock my video card
    It didn't occur to you that the OC was unstable?
    Zap
    Clan of the Bloody Fist

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    Default

    am i an idiot or did you not state what psu you have?

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