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Adding additional PSU's when running multiple GPUs

By Leeky · 15 replies
Dec 8, 2010
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  1. I've been doing a bit of research lately, because I'm unsure of the exact upgrade direction I want to take, and I've come up with the idea of using 3 full HD screens, along with triple SLI/CF, but the power requirements in my case would be above the capability of my Corsair HX-750.

    Having just spent £117 on that I'd rather not even consider replacing it. So can a system use a second PSU (like any decent PSU), or do they need to be built specially for the purpose?

    I was kinda thinking maybe it would be possible to run the system on my Corsair, including 2x GPUs, and then run the 3rd/4th using another PSU, like a 600w modular (thus only using a couple of cables) OCZ one or something.

    Besides the space requirements, how exactly do you go about doing this (e.g. how would you connect it into the motherboard), and is it physically possible? Do I need to use a booster thingy PSU like the ones Red uses in his hollodeck instead? If so, where on earth do you purchase them from in the UK, and what are they called?

    Its purely discussion right now, I'm not tying myself down to any particular idea, I'd just like to understand all my available paths, and answer a couple of questions I'm unsure about more than anything.
  2. MrTLee

    MrTLee TS Rookie

    I'm no expert in PSU's so I wont bull**** you on that, it's my weak spot, but is it possible to use multiple PSU's on one system? Yes. Both in your case? I don't know.
  3. red1776

    red1776 Omnipotent Ruler of the Universe Posts: 5,073   +164

    boy have I got an answer for you Leek, :)
    I have 3 psu's in mine, see specs fhttps://www.techspot.com/gallery/member-galleries/p4037-here-ya-go-supersmashb.htmlor the models

    *** here i looked it up for ya
    http://www.newegg.com/Product/Product.aspx?Item=N82E16817104054&Tpk=fsp booster x5
    I very highly recommend them. very clean, 85+ efficiency/500w/40A/4-rails low heat, and ultra low ripple. you could run both 460's of of it. I have been using them for a few years now.I have four HD 5850's sharing 3 of them , and then my main unit the Corsair HX 650W for the MB and peripherals. I have had two 180w HD 5850's sharing one of these units with no problem. The ripple rating on these things is stellar, 13mv at 80% load!
  4. Leeky

    Leeky TS Evangelist Topic Starter Posts: 3,357   +116

    OMG, is that all it is Red?!? I was expecting like $300+ for one. :haha:

    So its "hollodeck" certified and tested then eh? :D I knew you'd see this and reply. So for the sake of argument, would this happily provide power for 2 GTX580's (which is about the highest possible power draw I can think of, off the top of my head right now)? I just wanna get an idea of the limitations of them when powering 2 cards really, as power measurements include the system usually.

    I really like the idea of 3x 24" LCDs (Been the two route already and ones bust!), but I'd prefer to give each LCD its own GPU if I'm gaming (not essential I know, but I like the idea), and the full stop hit me when I realised recently you couldn't triple CF HD6870's, nor triple SLI GTX460's. Annoying, because these are more than I needed at full HD. So I'm looking for other options that can be triple CF/SLI, that would work well with triple LCDs at full HD gaming resolutions, that will also work with some of the gear I already have e.g. my new PSU.

    Since you have them already, looking at the pictures, does it take the switched feed from a spare molex plug (I can see a molex plug on the back of it), so it knows when the other PSU is running and it should as well?

    Its definitely something to consider - At that price even ordering from the US and paying duty on it here in the UK isn't an issue.
  5. red1776

    red1776 Omnipotent Ruler of the Universe Posts: 5,073   +164

    Hey Leek,

    well to answer the first, I would only run 2x 220w max TDP cards on it, so you could go 2x 5870's or 2x GTX 470's/570's
    and yes, you just plug in a spare 4 pin molex from the main PSU to feed it the signal from the bios. These are great units, I am surprised as well that a 500w FSP unit isn't much more as well. if you can find em, or get one there I definitely would. There are a few reviews about a high pitched noise from the unit. i have used and built with 13 of these things, and not had that happen to date.
  6. Leeky

    Leeky TS Evangelist Topic Starter Posts: 3,357   +116

    Hey Red,

    Thanks for the explanation. Are the 5870's not due to be replaced by the 6950's, or something like that shortly? I can never get my head around all these numbers - so if I'm way off the mark you'll realise why! :haha:

    I dunno if I'm better off getting a HD5970 or the HD6970 (thats the twin GPU isn't it?) and running that with eyefinity, or whether a better bet is to spend more money and get 2-3 separate GPUs.

    A HD5970 is £422 (It would seem ebuyer.com and overclockers.co.uk have both pulled down the HD5970 in the last couple of days!)
    The XFX 5870 is £190 a pop.
    Unless I go for something like a GTX 470's and water cool them? They're £223 a pop, but include the cooler cover plate already.
    Hell I could even run dual GTX480 SLI with water cooling it shouldn't be an issue with heat).

    You see where the confusion is coming from now? :haha:

    I'm never going to be gaming at 2560x1250(or whatever) resolutions, the most I'll see is 1920x1080, so it seems a complete waste to spend money on a single GPU that can do that. But then I don't fully understand how multiple LCDs come into the mix. I know on the desktop it makes sod all difference (running 2x VA2216W4's taught me that), but gaming with eyefinity and the picture across all threee screens at the same time is surely going to kick it much harder than one single 2560x1250 LCd surely?

    Hence my thoughts of 1 GPU per LCD, and roughly double the rendering capabilities would suit it better. I'll be damned if I can think correctly now though, I've been studying all day, and reading up more and and more about GPUs during my breaks, and I'm just overwhelming myself now! :haha:
  7. red1776

    red1776 Omnipotent Ruler of the Universe Posts: 5,073   +164

    I think thats a good idea. you will be dealing with a resolution of 5760 x 1080 (1200) I think three 6870-6950's is in order. count the pixels man! count the pixels :) a pair of 580's or 6990's would do nicely as well!
  8. Leeky

    Leeky TS Evangelist Topic Starter Posts: 3,357   +116

    Could I in theory run a pair of 580's or 6990's with that booster and my HX750? I'm thinking it should be manageable assuming the booster just runs one single GPU, and my Corsair the other one.

    Also, I didn't think I could 3-way CF HD6870's? I'm sure you informed me of this previously? :confused:

    A pair of 580's would cost me around £860.00
    3 HD6870's around £630 (easily paying for the booster and postage with change to spare)

    Right now, if 3 HD6870's can do the job with performance to spare at max settings it seems a likely choice.

    The change difference is likely to be able to get me a new motherboard. Guess in the meantime I need to wait for the 6990's to see how they fair up. :) They're due anytime shortly aren't they? :D
  9. red1776

    red1776 Omnipotent Ruler of the Universe Posts: 5,073   +164

    opps Indeed, I meant 6970-6950's

    6990;s due in Jan
  10. Leeky

    Leeky TS Evangelist Topic Starter Posts: 3,357   +116

    OK, well I'll hang onto this until the 69xx are released shortly, then make a decision from the reviews on here. :)

    Thanks for your help Red. :D
  11. MrTLee

    MrTLee TS Rookie

    6800's can't go more than double. The 6900's should be able to 3-Way and have 2×DVI, HDMI, 2×mini-DisplayPort.

    Rumor is that release date for the 6900's is Dec.15th. Next week today.

  12. Relic

    Relic TechSpot Chancellor Posts: 1,372   +17

    Man you're really going all out I see Leeky :D. I'd put my money on the 6950 being the sweet spot for ya price/performance wise guessing it being slightly below the GTX 570 and 3-waying shouldn't be an issue. Shoot if AMD can pull off the crossfire scaling like they did with the 68xx on the 69xx maybe crossfired 6970's would fit you better.
  13. Leeky

    Leeky TS Evangelist Topic Starter Posts: 3,357   +116

    I'm undecided. I was going to purchase a new Mac Pro (well 3 months ago I would have been), but since I'm back into gaming now for the forseeable future I decided I might as well beef up my PC.

    Hopefully by the time I make a final decision the i7 core 980x will have reduced in price a bit more, as this would go nicely with my plans. I've already decided on the vast majority of my system, just waiting on the GPUs now. :) That said, I haven't seen the 980x even budge on price.

    I'll probably be having two christmas' this year. :haha:
  14. LNCPapa

    LNCPapa TS Special Forces Posts: 4,254   +512

    Not to rain on your parade Leeky but the EE versions of the Intel chips rarely drop in price. I think you'll be waiting quite a while for the 980X to come down to a "reasonable" cost. I'll be waiting alongside with you since it's currently my dream CPU.
  15. Leeky

    Leeky TS Evangelist Topic Starter Posts: 3,357   +116

    Seriously? I thought they'd dropped them all in preparation for the release of their new line-up (or AMDs, or something like that - I read it on here I think)?

    That's a serious bummer. :(
  16. LNCPapa

    LNCPapa TS Special Forces Posts: 4,254   +512

    Here's an example. You'll notice many of those that appear aren't even EE versions, but almost all of the ones that actually are have ridiculous prices even if they are very old chips.

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