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Thread: Need help with a PSU.

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    Default Need help with a PSU.

    Okay, I've asked this question around at least six different forums now, and I'm really struggling to get a satisfying answer out of people. But this place seems like the perfect place to ask about PSUs, so I'm hoping you guys can help me out. But please bare in mind, my knowledge of computer hardware is limited, and anything I know about computers has been learned over the last month or so of doing tons of research. Unfortunately I don't know too much about PSUs at this point, so please keep any explanations simple! Thanks

    So I'm building my first PC in just over a week, and it's intended use is for gaming mostly, but I'm going to be doing a bit of light video and photo editing (Sony Vegas/Photoshop) also. So far I'm settled on all the parts except the PSU.

    Here's the specs:

    Asus Z68 Pro Motherboard.
    i5 2500k OC to 4.7/4.8GHz.
    EVGA GTX 580 SC.
    8GB RAM (might try and lower the timings a bit on these).
    Noctua D14 cooler.
    Samsung Spinpoint F3 1TB 7200 HDD.
    OCZ Vertex 2 60GB SSD.
    A cheap DVD RW drive.
    Coolermaster HAF X case with one or two additional fans.

    Now what I need is help choosing the right wattage PSU for this setup. From what I understand, a PSU runs at it's most efficient between 50 and 60% of it's total power. So ideally, It'd be best to use a PSU that strikes a nice balance between say 30ish% idling and 70ish% under load (gaming) (wouldn't it?).

    I don't really have any use for Sli so there's no need to factor that in.

    I really hope you guys can help me. And any suggestions given, can you please give the rough percentage of the PSUs total usage at both idle, and under gaming load.

    I'd really appreciate the help. Thanks in advance

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    Quote Originally Posted by The New Black View Post
    Now what I need is help choosing the right wattage PSU for this setup. From what I understand, a PSU runs at it's most efficient between 50 and 60% of it's total power. So ideally, It'd be best to use a PSU that strikes a nice balance between say 30ish% idling and 70ish% under load (gaming) (wouldn't it?).
    Holy crap, FINALLY someone who can apply the "40-60% load efficiency peak) fact correctly! You have no idea how many people just double their peak wattage and and say "Dur, efficiency high at 50%!!!"




    Anyway, got a budget? Do you need modularity?
    It's my PSU in a box!
    Ooo-ooh,
    My PSU in a box, baby!

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    That Sandy Bridge i5 is really very power efficient. OC'd to 4.5 GHz (by setting the CPU voltage to 1.3, or even 1.35V), it will be satisfied with around 140W peak (that is, all 4 cores at 100%). I've seen this confirmed at several different places, and this is really good. The GTX580, especially when overclocked, is a different story. It will chew through a bit above 300W peak, which you can expect from synthetic benchmarks. A 260-280W peak is to be expected in Crysis 2, Metro 2033, Arma II, etc. The drives (HDD, ODD, SSD) will make due with around 30-40W when using all of them at the same time. The fans will take anywhere from 4W to 20W, depending on size and speed. This concludes the 12V power draw. The 5V rail won't see more than 50W of action, and the 3,3V one will take up some 30-40W. These are all peak numbers.

    To have a PSU taxed to 70% of it's max rating at your peak power draw, you're looking at taking a nice 750W PSU. However, these conditions will only present themselves when you benchmark/stress test all of the components individually, all at the same time, with a dedicated synthetic test. A much more reasonable figure will be 20-30% lower, so a good quality 650W unit will be more than adequate. So, if you intend on benching/heavy OC and regular folding/SETI/BOINC/unlocking phones/whatever, go for a 750W supply. If not, a 650W will be more than plenty.

    So, where will you shop for a PSU, and what is your budget? Is silence a big point on the checklist? (though I doubt it, the GTX580 can be a screamer) How about modularity? Tell us this, and we'll provide some more specific suggestions.
    Careful what you wish for... You just might get it.

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    Quote Originally Posted by Phaedrus2129 View Post
    Holy crap, FINALLY someone who can apply the "40-60% load efficiency peak) fact correctly! You have no idea how many people just double their peak wattage and and say "Dur, efficiency high at 50%!!!"
    Really? people don't know this stuff? As I said, I really lack knowledge with computer hardware, but I found the efficiency percentage quite easy to grasp.

    Now you've gone and made me feel all clever

    Quote Originally Posted by McSteel View Post
    So, if you intend on benching/heavy OC and regular folding/SETI/BOINC/unlocking phones/whatever, go for a 750W supply. If not, a 650W will be more than plenty.
    Apart from the CPU, the GPU is already overclocked a bit (superclocked? it's the SC version). I don't know if lowering the timings on the ram will count as an overclock, as in, taking more power. Though apparently the Asus mobos like the RAM at 1.5v (not sure if this is true), so if lowering the timings affects that, then I'll leave the RAM as is. With that said, is that still fine for a 650w? or would you recommend 750w?

    ------
    ------

    As for the PSU itself I'm feeling good about the Seasonic X Series range. Though I'm a little confused about them. I see the older versions (the 650w and 750w) are being phased out for the newer ones (660w, 760w etc.) but is there any real difference between the older models and newer models apart from the added 10w? What I guess I'm asking is, are they just as efficient as they older ones, or better?

    Thanks for the replies so far, I really appreciate it

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    For you, there is not really going to be a tangible difference. In terms of performance, they are most the same as well.

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    I already accounted for the GPU being (factory) overclocked. As for the RAM, it's a minor concern - it gets it's power from the 3.3V line, and it rarely uses more than 5A per stick max. This is nearly regardless of the speed and latencies, and the power usage goes up very little when overvolting it, but it's really secondary all the same. RAM basically has the 3.3V rail all to itself, so don't worry about it.

    As for the 650/750 vs 660/760, the difference is small, but it's there. Improved soldering, somewhat better regulation and negligibly better ripple/noise suppression, as well as a bit more relaxed (quieter) fan settings, from all that I could gather. Still the differences are within the margin of error of measurements, so it's really not that important. If you can catch a good deal for a PSU of the previous revision, go for it.

    650 (660)W will be enough, but if the price difference proves to be inside 10-15% range, go for the larger unit.
    Careful what you wish for... You just might get it.

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    Quote Originally Posted by McSteel View Post

    As for the 650/750 vs 660/760, the difference is small, but it's there. Improved soldering, somewhat better regulation and negligibly better ripple/noise suppression, as well as a bit more relaxed (quieter) fan settings, from all that I could gather. Still the differences are within the margin of error of measurements, so it's really not that important. If you can catch a good deal for a PSU of the previous revision, go for it.
    .
    The 660w is only £5 more, so I might aswell go for that one.

    Quote Originally Posted by McSteel View Post

    650 (660)W will be enough, but if the price difference proves to be inside 10-15% range, go for the larger unit.
    Just to clarify, you meant 'the larger unit' as in the 660w (over the 650w)? or 'larger unit' as 750/760w?

    Thanks for the reply. That one little question aside, you've actually helped me more than everyone else from the other forums combined by actually explaining things to me. I appreciate it

    EDIT: Also, I want the PSU to be future proof for a good few years, meaning, I'd hope it to run some of the more high-end GPUs of two or three years time. Do you think things might move on beyond the power capabilities of a 650/660w PSU at that point? or should a 650/660w last me for the next 1/2GPUs I buy? Thanks again.
    Last edited by The New Black; 05-30-2011 at 10:40 AM.

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    Future proofing is like playing three card on the street.
    Expectations are requirements will lessen. I read it if the 750/760 prices are within 10 or 15% it won't hurt.
    I can see you adding more storage or Blue Ray, and/or wireless functions. Neglegable
    If 3D takes off requiring new cards who knows?
    Sortware "might take a jump" in CPU usage. Again minor.?

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    As for the 650/750 vs 660/760, the difference is small, but it's there. Improved soldering, somewhat better regulation and negligibly better ripple/noise suppression, as well as a bit more relaxed (quieter) fan settings, from all that I could gather.
    New X series seem to catch up in transient response tests as noted by TPU reviews of Corsair AX850 and X-460FL.

    If difference in price is indeed small, I'd go for it.

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    Yeah, I meant go for 750/760 if they're within 10-or-so % of the 650/660, price-wise. The original X-series models are great, the refresh is just a bit more polished...
    Careful what you wish for... You just might get it.

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