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Can a PSU be too strong for a rig?

I'll get right to the facts.

I have a pre-built computer with a 220W PSU, it runs games fairly well, but I got myself a smallish graphics card to help give it a boost in gaming. Long-story short, the graphics card drew too much power and crashed my board (I couldn't even turn the computer on until I performed a BIOS reset). I left the graphics cards aside for now, but about 3 or 4 weeks ago something similar seemed to happen. The computer shut down and wouldn't turn back on. I didn't have to pull a BIOS reset this time, I just yanked the optical drive out and it seemed to work. I worry that my PSU is dying though, so I've got a bit of urgency to replace it now.

I probably don't need much more than 300, but if I'm going to buy one... I figure I should get one that will last. I want to get myself something I might be able to put into a self-made rig one day, something big and beefy and modular, with 750 Watts. My worry is what will happen if I plug this thing into my little pre-build mobo that's used to using 220W. And even if the mobo can handle it, what happens to the extra 500 watts, do they dissipate as heat? Or does the PSU really only generate what is needed?

I performed a test by yanking the power wires connecting from my PSU to my motherboard (after I had shut it all down of course). I've never switched a PSU before and I wanted to see if I could get this right at least. I waited a few minutes, plugged it back in, and the computer turned back on again but something was weird with it... it acted similar to how it did when I pulled the BIOS reset. The clock reset to the factory settings (January 1st 2010), and every window I opened had a stuttering lag to it. Also the lower-right icons in the tool-bar all turned invisible. It wasn't serious, like last time it happened I just did another reboot and it went away. But I just worry if this is some kind of... sign, that messing with my computer's power supply is walking a fine line. Or if it's not at all normal and I have some serious problem with my mobo.

By the way, these are the two PSUs I'm hesitating between. I figure that... for 10$ more I should go for the 750W one. Both are fully modular too, why I want them.
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  1. The rating on a PSU is its maximum power - it won't be generating that much all the time, only as much as the system needs. So, in other words, no, there is no such thing as too much of a PSU for a system, aside from the fact that a really heavily overrated PSU will probably not be as efficient as one properly sized for your system (since PSUs are not terribly efficient when operating at low load).
  2. I heard somewhere that say, for example, my computer rig is pulling 350 W. A PSU that's rated at 700W will generate more heat plugged into my rig than a similar PSU rated at 400W would. I don't know about electrical or computer engineering to know if this is true or not though...

    I'd be totally willing to spend extra to get the beefier unit, but my case doesn't have THAT much cooling. Not enough to handle 700W of thermal dumping.

    If it is just smarter to only get power for what I need, I was also eyeing this one. It's in the same price-range as the other two, but gives out 500W, and is gold certified. This is sure to produce less heat and (from what I read in the reviews) less noise too.
  3. Best answer
    It may be a little less efficient, as cjl says, and that's where the little extra bit of heat will come from, but it definitely won't be a problem. The PSU pulls what it needs, plus a little more that gets dissipated. Here's how the efficiency rating of a PSU works: when an 80% efficient box needs to provide a certain amount of wattage to a system, that wattage is 80% of the power that it pulls from the wall. When an 80% efficient PSU must provide 80 watts, it pulls 100 and the extra 20W is dissipated as heat.
    A list of 80 PLUS ratings
    An efficient, high-quality 750W unit probably generates less heat than a cheapo, generic 220W one.

    The PSU that you get now will depend on the GPU that you get in the future. There's very little out there that uses more than 500W on a single card. Are you going to go SLI or get a 580? If not, go 500. This one's much cheaper:
  4. as a side note of efficiency. power supplies do horrible when running at 1/4 of their max output or less. they also do bad in the last 25% of its rating. but not nearly as bad.

    here are a few examples of this. along with way more info than you need if you want to read the whole article.
  5. i have 850W psu 80+ and never had any problems with it. there are some other things that pull power ,like HDDs,DVDs,soundcards, overclocked cpus,overclocked gpus. make the math how much wattage each of them will need when on max, sum them and this should give you a good idea what you should look for.
    In my case i really dont need that much of a psu but is good to be ready for crossfire or sli if needed !
  6. The CPU and GPU are basically the only components that matter. I doubt everything else'll pull 30W total.
  7. pointless really. the system would never be big enough to warrant such a big psu...
    get a cheap 350w to power the current system and gfx and sit back and enjoy your games... then start saving. for a entry level i3 setup, your looking at 350, for an i5 setup midrange should top out at no more than 1000, or an i7 setup where the skys the limit on how much you want to spend. coz by the sounds of it your system is either pretty old or is a basic media pc,. when i say basic i mean something like a low end dual core with 1-2 gigs of ram and something like gma 945 for gfx (with out your card)... if it eather of them then im sorry to say there not really worth the money to upgrade. better to think about an entire new build...
    so m8 just buy the psu that you need rather than what you think you need...
  8. kajabla, a full featured motherboard and RAM will pull 60 - 100 watts by themselves.
  9. kajabla said:
    The PSU that you get now will depend on the GPU that you get in the future. There's very little out there that uses more than 500W on a single card. Are you going to go SLI or get a 580? If not, go 500. This one's much cheaper:

    I doubt I will get an SLI, or even overclock for that matter. And while that one is very nice... it's not at all modular. I worry that my case might have a few tight squeezes, and getting a modular unit will (I hope) help to use the space I have the best I can.

    Oh and thanks for all the input guys, I'll read them all in further detail (along with farrengottu's article) when I get back. But now I'm off to work.
  10. I will say this in simple words:

    1- Can a PSU be too strong much for a rig? Yes
    2- Can a PSU that's too much for a rig kill the system? No
  11. Sure, modular. It's all good.
  12. jsc said:
    kajabla, a full featured motherboard and RAM will pull 60 - 100 watts by themselves.

    Motherboard and RAM = 100w, yeesh you're not even trying! :lol:
  13. @ HEXiT
    I can understand the wisdom in this... basically to just stop trying to sup-up my current crapper and invest in a real gaming computer, but the sad reality is that I don't have enough money to buy a real gaming computer right now. I could start buying the pieces, but I wouldn't be able to afford all of them. So I figure, rather than build half a computer and have it be stuck in limbo for 5 months, why not start by buying pieces that will be compatible with my current pre-built, and with my future rig. Namely a better case and a nice PSU.

    My main concern is simply that there might be an obscure fault with some motherboards where suddenly switching PSUs can cause it to malfunction catastrophically. But... worst case scenario, if that does happen I just need to kick myself, tighten my belt, and settle on starting to shop for the new computer. I do have 900$ or so, but I was hoping to save more like 1200$. Also I don't necessarily want to spend 100% of my savings on this, there's more to life than just gaming, lol.

    But yeah, if you guys tell me that the odds of a mobo failing from a PSU swap is slim to none... I'll be comforted and get the new unit.
  14. Any good PSU will provide close to exactly the same power. This is not a person we're talking about; if the parts get the current they need, they'll work. Parts can't get used to each other, and they can't miss each other when they're gone. Don't worry about it.

    $900 will get you a 2500K rig with a fairly bad GPU, but $1200 will come closer to something that deserves the CPU. There's a little bit of limbo right around there.

    What's your current case? Expensive cases aren't necessarily much better; you may well be totally fine with the one you have.
  15. kajabla said:

    What's your current case? Expensive cases aren't necessarily much better; you may well be totally fine with the one you have.

    Oh trust me, it's not just about getting better cooling. Like HEX guessed, I got myself an HTPC for my prebuild, I thought it would be nice and discrete and that I could just use microATX pieces. I figured that computer miniaturization had reached the point where small mobos were sufficient. I didn't realize this thing doesn't even use mATX, it uses "DTX", and a VERY weird PSU. That PSU is now failing (from what I can tell), and I can't find any others for sale in that form-factor. So... yeah, I'll need a case that supports normal PSUs.

    Long story short, I'm going to start my new rig by shopping for a case and PSU, and while I wait to buy the rest I'll use those 2 with my old build. I won't go crazy either, I'll probably get the Core 3000, I heard good things about it, it's ~70$.
  16. Choose your case by stylistic preference. Most over $60, and many under, will perform perfectly well. If you like the look of the 3000, go for it.
  17. Well I liked the look of the Level 10 to be honest, but I'm not going to break the bank for a case, lol. I mean I have the money, but like you said earlier... the less money left over for the actual hardware... the worse the gaming experience will be. I'm still not sure what my mobo will be (I'll create a thread dedicated to that when I come to it), but I know I should save the bulk of my money for the graphics.

    PSU is important because it supports everything in the case, so I'll spend that little bit extra for a nice gold certified.
  18. Best answer selected by PTNLemay.
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