Is 750w PSU Really enough?

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KoutaFG
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I gotta replace my power supply on the 20th of this month, I've been told that 750w should be more then enough but I don't entirely believe that, cause the video card I currently have, newegg said that if I have two of them that I should have a at least 750w PSU but I also prefer fan cooling over liquid, so I have a total of 5 120mm case fans, 3 of them being high powered, I think 3800 RPM each, always running at 100% and one 220mm side fan, the other things in my computer are,

two hard drives, one 500gb and the other 400gb, 8 gigs of ddr3 1600, a 5 fan touch screen controller that's powered by the PC's PSU and my ATI HD 6950 OCed I think, at least I think it came OCed from newegg, that I plan to get a second one of, for crossfire.

I know how to build a PC but I haven't done it enough to know all the facts so, hints why I love this site.

Any help/info/facts would be nice, thanks!

ASRock 990FX Extreme3 CPU: Phenom II X4 945e 3.0 Ram:(2 x 4GB DDR3 ) GPU : HIS 2GB 6950 PSU: Corsair 850w

Allen86
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A 650 watt from Corsair, PC Power & Cooling, Antec, or Seasonic is more than enough with plenty of overhead. AMD and Nvidia put rather conservative numbers on their PSU requirements and don't necessarily reflect real world power usage. Basically, you can just say they're thinking the end user has a ineffecient PSU totally loaded down with stuff, then yeah you'll probably need a 750 watt to make up the difference of it wasting power and running hot under load.

You could Crossfire 2 6950's with a good quality bronze 650 watt or even run your system off a good quality 550 watt as is (your single gpu). Your case fans, controller and hard drives don't really pull much juice, you'll be fine with a 650 watt, 750 watts is overkill IMO unless you're wanting to crossfire later and have a lot of overhead just to give you a warm fuzzy feeling lol.

Some people will tell you that you need like 850 watts or something, they have no idea what they're talking about..or they're just the type of people who like to buy in excess, who knows. I remember when I was buying my PSU (TX 650 v2) I was asking opinions about it on another site, and a couple guys there were trying to tell me I needed an 800 watt PSU...which is quite honestly, ridiculous for my setup that pulls maybe about 300 under load at the wall. I upgraded my PSU though for a GPU upgrade later on, even then it'll still only be 350-400 watts maximum I'll even be drawing. Just saying, be careful who ya listen to, people on the net are full of misinformation and love to blow your money for you.

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KoutaFG
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Ah, well, I'm looking at CORSAIR Professional Series HX750 (CMPSU-750HX) powersupply, I think it'll be the one I go for on the 20th, its a silver 80+ rated PSU.

I just didn't know if the Nvidia and ATI gives you those numbers, thinking your system is using just the basic hardware or if they think your system has a lot of extra stuff.

hellblazer55
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ATI and Nvidia give you numbers based on Intel setups which is always misleading.

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Razear
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High quality manufacturers like Corsair actually underrate their PSUs so a 750W model may actually be able to output 850W and so on. The PSU requirements listed by AMD and NVIDIA are tested using generic PSU models since that's what the majority of people are using.

HuXDestroyS
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@Hellblazer55, love the picture.

On my turd of a PC now, I run 8gb of RAM, two 1tb hhd's with a 2.8ghz processor on a I want to say a 250w PSU. And mine doesn't even hiccup. I don't have the video card, or anything overclocked, but I wouldn't think 750w is too little. I don't think more would hurt but in my opinion you should be fine.

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Allen86
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I'd be willing to bet your PSU won't draw more than 450-500 at the wall, and that's stressing your entire system to the max. If you really want to know what size PSU you need, spend 15 bucks and buy a kill-a-watt meter.

Either way, if you're set on the hx750 just buy it then. It's a good psu.

KoutaFG
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Yeah, I was able to buy the Hx750 last night, of course its the weakend, so I still gotta wait more then the 3 day shipping.

but at least I'll have my system up and running again soonder then I thought I would.

On a second note, I'm getting this new PSU because currently, my main system has been shutting off nearly randomly, though usually when I'm playing a game, though I've had it shut down seconds after I got into windows but that was after it had shut down after playing a game and then booted back up on its own.

What's odd, is that this has been happing for the past mmmm 5 days, and I've had a day or two where it didn't shut down once, even though I played games all day those two days, that's what made me think it was the PSU, sense I never got any temps above 60c on anything.

But if it turns ot that the PSU was not the issue, what's the next possible part that's causeing this?

Allen86
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Could be something corrupted in windows causing it, could be something in the bios being screwy, could be your PSU, could be a driver issue, could be alot of things. With stuff like that, its process of elimination. Start off with the things that don't cost you money, like reinstalling all your drivers fresh, repairing or reinstalling windows, resetting your BIOS (jumper on the mobo), checking to make sure all your connections are secure. Try running some different ram, switch out the PSU with another PSU you have laying around, etc etc.

KoutaFG
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Allen86 wrote:Could be something corrupted in windows causing it, could be something in the bios being screwy, could be your PSU, could be a driver issue, could be alot of things. With stuff like that, its process of elimination. Start off with the things that don't cost you money, like reinstalling all your drivers fresh, repairing or reinstalling windows, resetting your BIOS (jumper on the mobo), checking to make sure all your connections are secure. Try running some different ram, switch out the PSU with another PSU you have laying around, etc etc.

Sadly, I do not have extra parts that'll work with this system to rule things out, I upgraded from ddr2 to ddr3, replaced the mobo and ram and the current PSU is the only one I have, at least until the new one comes in the mail but I guess, I'll just have to wait for the new PSU and if the issue continues, I'll format my computer and go from there heh. I had a feeling that someone would say that.

Allen86
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Well, what else is there to say, there's no magic button that you press that's labeled "FIX NAO" :)

KoutaFG
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Allen86 wrote:Well, what else is there to say, there's no magic button that you press that's labeled "FIX NAO" :)

If only their was. . . . Or at least some characteristics, that allowed you to at least lean towards one part and not the other, so that its not a complete guessing games heh, if my issue is not the PSU or a software issue, I'm screwed x_x

Allen86
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Something to try, not sure if it will fix your issue or not, but atleast it won't cost you anything. Unplug it from the wall, push your power button in for about 10-15 seconds. Take out the bios battery for about 5-10 minutes then put it back in, can jump the CMOS as well if you like, same difference I believe. Probably wont do anything for you, but its worth a shot. Usually this fixes issues where the system isn't detecting hardware properly in the BIOS and wont allow it to boot causing it to start and restart in a cycle.

Had this happen to me recently after I blew the dust out of my system, computers have strange personalities..apparently mine hates baths.

KoutaFG
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Allen86 wrote:Something to try, not sure if it will fix your issue or not, but atleast it won't cost you anything. Unplug it from the wall, push your power button in for about 10-15 seconds. Take out the bios battery for about 5-10 minutes then put it back in, can jump the CMOS as well if you like, same difference I believe. Probably wont do anything for you, but its worth a shot. Usually this fixes issues where the system isn't detecting hardware properly in the BIOS and wont allow it to boot causing it to start and restart in a cycle.

Had this happen to me recently after I blew the dust out of my system, computers have strange personalities..apparently mine hates baths.

Maybe your computer is some kind of cat,

but I'll give that a shot, could be that I just need to update my bios, I haven't done so yet, its running what ever bios it was shipped with but first, on the 15th, when my new PSU comes in the mail, I'll test that out first, hopefully that's all I'll have to do.

Its odd, every thing was running just fine for about a month or so, then this all started to happen. Its not like I got some new hardware then this started to happen, the system seems to shut down when ever a good amount of strain is on it but once, it shut down while playing a game, then about a minute later it started it self up, then seconds after it booted into windows, it shut down again, though I can't remember if it attempted to start back up again after that. in any case, I'm gonna see if the new PSU fixs things before I try anything else.

Allen86
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Wouldn't hurt to run a check disk on the drive, may have some bad sectors as well.

KoutaFG
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Well so far so good, I put the new PSU in and have yet to shut down with out notice, though the past psu was able to go a day randomly with out shutting down, so I won't know if I've fixed the issue until about 3 days of use with this new psu.

Wish me luck heh, its done a full day so far.

TheRealMan
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Well, if you really want to check, you can use a program like HWMoniter and stress your system 100% and check the voltages. If your pushing your system too hard your voltages will drop noticeably. Also, keep in mind that a higher quality power supply will almost always cut out and shut down if you push it to hard to save your system from damage.

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KoutaFG
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TheRealMan wrote:Well, if you really want to check, you can use a program like HWMoniter and stress your system 100% and check the voltages. If your pushing your system too hard your voltages will drop noticeably. Also, keep in mind that a higher quality power supply will almost always cut out and shut down if you push it to hard to save your system from damage.

Well I have my new PSU in and its been about 2 or 3 days and my system has yet to shut down on its own, so I'm guessing it was my old psu, kicking the bucket, I'm using my system the same as I was with the old psu so its under the same amount of load as back then, so hopefully I've fixed the issue, though I don't feel completely out of the woods just yet, the old PSU had a random streak where it didn't shut down on its own for one or two days so, there is still a small chance that something else is wrong, only time will tell.