SLI on dual psu

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  1. Posts : 123
    windows 7 x64
       #1

    SLI on dual psu


    i'm planning to setup an SLI of two gtx570's

    i currently have tx650w. enough to power up one gtx570 card.

    what wattage should I add to power up the second GPU?.

    as I've searched in nV. the power consumption of gtx570 is 219W.

    would another 300W PSU be able to run the second gtx570?.

    what will happen if I SLI two cards with the same gpu core. but with different clock speeds?.

    can I overclock SLI setup cards?
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  2. Posts : 4,517
    Windows 7 Home Premium 64bit
       #2

    The SLI configuration will default to the slowest Clock speed of the two, as well as VRAM available as the lowest of the two.

    So if:
    First 570 has clocks of 732 and 2560 VRAM
    Second has clocks of 797 and 1280 VRAM

    The 2 in SLI would run at 732 with 1280Mb VRAM.


    I would just upgrade your power supply to a single more powerful one.
    Two SLI 570s will pull around 420-440W at Maximum load.

    Depending on your setup, and how much you will overclock the GPUS, a really good quality 750W will work.
    850W if you want to play it safer more headroom, or if you plan on heavily overclocking them as well as the rest of the system.
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  3. Posts : 799
    Windows 8 Pro 64-bit
       #3

    Wishmaster said:
    Depending on your setup, and how much you will overclock the GPUS, a really good quality 750W will work.
    850W if you want to play it safer more headroom, or if you plan on heavily overclocking them as well as the rest of the system.
    I'll agree with this.
    You gotta remember; for the most part, PSU wattage listings are their peak wattage; running a PSU close to its peak wattage is definitely not good for its life.
    I'd personally suggest going safer. You never want to skimp out on your PSU.
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  4. Posts : 123
    windows 7 x64
    Thread Starter
       #4

    we'll talking about safer operation..

    will having two PSU's be more safer?. since it's cheaper because I already have the 650W PSU.
    and having two PSU won't stress both of them since they will have 2 sources of power.
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  5. Posts : 2,606
    Windows 7 Pro X64 SP1
       #5

    4hya said:
    we'll talking about safer operation..

    will having two PSU's be more safer?. since it's cheaper because I already have the 650W PSU.
    and having two PSU won't stress both of them since they will have 2 sources of power.
    Regular PSUs are intended to work only while connected to a motherboard. I believe that it's possible to overcome that, but I've not done it.

    Some manufacturers (Thermaltake is one) make secondary PSUs that are intended just to power graphics cards for SLI. One that I see listed (W0158RU) wouldn't give much of a cost savings over a decent regular supply.

    If you're looking for a PSU certified by nVidia, see here:

    Build an SLI PC - Certified SLI-Ready Power Supplies

    I don't see a listing for dual 570s, but it may be similar to dual 470s. (The weakest PSU I see on the list is 700W, from FSP.)
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  6. Posts : 123
    windows 7 x64
    Thread Starter
       #6

    please refer to this one..
    Code:
    http://tomorrowsgaming.com/content/attachments/1529t-dual_psu_mod_diagram.jpg.html?cid=23
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  7. Posts : 2,562
    windows 10 pro 64 bit
       #7

    I actually run dual psu's one runs off the motherboard and powers the motherboard, C drive, and the 5850....the other runs the cd/hard drives....the secondary psu has a jumper wire between the power good and a ground.....the only problems are....finding (or building) a case that takes dual psu's....the fact that the secondary psu stays on constantly (unless switched off), or finding (or wiring a cable to conjoin) the psu's....and the temptation to rob one of the psu's to fix another computer.....on the plus side two good quality 500-700 watt psu are cheaper than the 1000-1200 watt psu....(at least at the quality level that I would trust)

    I would at least find a secondary that has the proper cables.....not many 300 watt psu have that....
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  8. Posts : 123
    windows 7 x64
    Thread Starter
       #8

    so that means.. I have to find a PSU that would at least have 2 6pin PCIe cables...or can I use the molex to PCIe connector to the second PSU. since it won't be stressed out by just running one gtx570 card.
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  9. Posts : 2,562
    windows 10 pro 64 bit
       #9
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  10. Posts : 4,517
    Windows 7 Home Premium 64bit
       #10

    Yes, dual 470s and dual 570s will be very close to each other on that SLI list, so the 470 list is the ideal place to look, since the power draw is about the same.



    Honestly, I would stick with a single PSU. It will likely be a better option, and cost about the same by the time its all said and done.
    Plus, you'll have a good quality 650 Corsair as a backup unit.



    I actually just went through alot of research on this subject. Basically I decided I wanted to SLI AFTER, I got my PSU. A Seasonic x750.

    Turns out, its plenty of power and the Average 570 SLI will not pull but around 650-700W under a heavy gaming load (with OCd CPU)
    Note: Thats at the wall. Which comes out to about 620W the systems is actually using, on the high end given a 88% efficient PSU.
    Which is at the 650Ws limit, and not at all good for long term. But well within the limits of a good 750W.


    Granted, if you do something like Prime 95 plus Furmark at the same time (and Furmark will use far more power than you could possibly use in any real world situation) it will be pushing close to its limits.
    But outside of a benching/stability session, how often do any of us do that?




    As I mentioned before, if you stick with the good quality PSUS Corsair, Antec, Seasonic for example, youll be fine.
    (( From what Ive seen Corasirs AX series is basically the same PSU as the x750 Seasonic))

    But ... if you plan on overclocking the snot out of both of those GPUS, you should certainly look at something a bit bigger. A 850W would fit the bill nicely for heavily overclocked 570s, and a Nice OC on the CPU.





    At any count, Corsair TX,HX and AX 750/850 PSUs are on that list.
    I would certainly be looking into one of these, rather than dual PSUs. I really think a single PSU will be better overall.



    Sorry for the book.
    Last edited by Wishmaster; 18 Nov 2011 at 08:24.
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