How low is too low on 12V rail?

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How low is too low on 12V rail?

Postposted on Mon Apr 29, 2013 11:38 am

So my PSU is this one...
http://www.newegg.com/Product/Product.a ... 6817139005
Corsair 650Watt PSU that's about 2.5 years old now.

I knew that my sensor readings were way off with HWmonitor reporting 8.4 volts for the 12V rail, and speedfan reporting 10.4Volts but I never really checked the actual volts with a multimeter. Maybe I just trusted the "corsair" name (with it having active PFC and other "features") so I never bothered but when I checked it with a calibrated multimeter the 12V rail was showing 11.55 Volts.

It seems a bit "low". It's within +/- 5% so it wouldn't hurt anything as far as damaging the hardware goes, but it's way off of +/- 3% spec so maybe it's part of the instability I'm seeing with the 7970 that I have? (viewtopic.php?f=3&t=87559)

I've seen voltages low like 11V or under 11 volts can cause some major problems, but with voltages just 450 millivolts off spec I don't have much experience, so could that be a source of the instability?

Also during Load / No load the voltages on the 12V doesn't change, it stays at 11.55V even maxing out the graphics card and the CPU so it's not caused by voltage droop from not enough capacity or anything like that.

So, what do you guys think? Should I replace the PSU with something better or call up corsair? It's still under the 5 year warranty too... If I were to replace it, what do you guys recommend? Should I also check the 5V rails too?
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Re: How low is too low on 12V rail?

Postposted on Mon Apr 29, 2013 12:13 pm

According to ATX 2.3, spec of your PSU, the specs for +12V are between +11.40 V to +12.60 V. However you are still on the low side and it should not be that low. From the reviews I looked at the +12V was not as low as yours. Granted they were probably new PSUs. I would ask Corsair on their forums if you can apply for an RMA. I've had excellent service with them. If you were to get a new PSU, I would look at new platinum certified ones. What hardware do you have to run?
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Re: How low is too low on 12V rail?

Postposted on Mon Apr 29, 2013 12:30 pm

GeForce6200 wrote: What hardware do you have to run?

Well the most power consuming hardware on my computer is the radeon 7970 1Ghz edition and the core i5 2500k @ 4.0 Ghz.
Another thing that's concerning is that the PSU gets really hot when it's under full load... the exterior of the PSU feels like it's getting to about 45-55C so it's much hotter inside.... and the fan barely moves air.

Yeah I don't experience any crashes except when I run any bitcoin mining program while I am gaming.... and it doesn't even matter what kind of game, just any 3D game. I originally thought it was any DX10/11 game but even DX9 or DX8 games causes a crash if I run it concurrently with a bitcoin mining program even if I underclock the GPU to 700 mhz. Running either by themselves is completely fine and completely stable for weeks and hasn't crashed yet. I can even bump up the clock rate on the GPU to 1130 Mhz while mining with no problems.

I also read somewhere that the 7970 is a lot more finicky than the 6870 when it comes to voltages and vRAM temps. The 6870 is what I had before and never experienced a crash with the same PSU.
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Re: How low is too low on 12V rail?

Postposted on Mon Apr 29, 2013 12:35 pm

I use +/- 10% on 12V & +/- 5% on all other rails as my rule of thumb.
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Re: How low is too low on 12V rail?

Postposted on Mon Apr 29, 2013 12:44 pm

Your current PSU should not be that hot under load. I have a HX-650 with 52A on the +12V as well and even under load it does not get that warm. The fan will slightly spin up. Your CPU TDP is 95W if I remember correctly, and even your mild OC should not pull as much as my FX-4170 with its 125W TDP. My GTX 580 will pull another 80 watts under load than your 7970 according to TR's own review. I have not used a multimeter to test my PSU. But all software reports around 12.00-12.11, though I take software readings with a grain of salt. Is it stable under every scenario except mining and gaming?
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Re: How low is too low on 12V rail?

Postposted on Mon Apr 29, 2013 12:55 pm

GeForce6200 wrote:Your current PSU should not be that hot under load. I have a HX-650 with 52A on the +12V as well and even under load it does not get that warm. The fan will slightly spin up. Your CPU TDP is 95W if I remember correctly, and even your mild OC should not pull as much as my FX-4170 with its 125W TDP. My GTX 580 will pull another 80 watts under load than your 7970 according to TR's own review. I have not used a multimeter to test my PSU. But all software reports around 12.00-12.11, though I take software readings with a grain of salt. Is it stable under every scenario except mining and gaming?
The software reports all kinds of weird numbers from 8 Volts to 10 volts.... nothing even remotely close to 12V, so I don't trust them. Yeah, it's completely stable doing anything except for when I mine and game concurrently. When I had a 6870 on the system, it was 100% stable and even doing mining+gaming never crashed it. Even a liberal estimate will put my overall power consumption to about 350-400 watts at maximum possible load with my current setup, which is only about 61.5% of the PSU's capacity. So, yeah it probably shouldn't get so hot.
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Re: How low is too low on 12V rail?

Postposted on Mon Apr 29, 2013 1:01 pm

Any way you can borrow a psu to test your system out? I think amazon has a decent return policy if it turns out the culprit is not the psu. Corsair's turn around time was very quick when I had to rma my HX-520.
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Re: How low is too low on 12V rail?

Postposted on Mon Apr 29, 2013 1:22 pm

I have an old 500W PSU laying around. It was working when I took it out so it should still work. IIRC, the voltage on the 12V rail was about 11.7 ish under full load... Not sure if it has enough amps on the split 12v rails to power the 7970 tho, I have to check when I get home.
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Re: How low is too low on 12V rail?

Postposted on Mon Apr 29, 2013 1:46 pm

CB5000 wrote:I have an old 500W PSU laying around. It was working when I took it out so it should still work. IIRC, the voltage on the 12V rail was about 11.7 ish under full load... Not sure if it has enough amps on the split 12v rails to power the 7970 tho, I have to check when I get home.

You could try tripping the psu with a clip, and have it just run the 7970 while the Corsair runs the rest.
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Re: How low is too low on 12V rail?

Postposted on Mon Apr 29, 2013 2:52 pm

I don't trust Windows monitoring software on my current machine. It's a Gigabyte Z68 board, and in Windows it always shows like yours - 8.something on the 12v rail. In the BIOS it shows 11.75ish all the time. The system is very stable, runs cool and quiet, and does not give me problems. So I don't worry. Like you, I also have a Corsair PSU.

Now if you are actually experiencing symptoms related to a bad PSU, like crashes or drives disappearing, then for sure I'd phone them up and RMA it. If you're not, I'm not sure it's worth pursuing.
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Re: How low is too low on 12V rail?

Postposted on Mon Apr 29, 2013 3:15 pm

Do you have a multimeter?
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Re: How low is too low on 12V rail?

Postposted on Mon Apr 29, 2013 3:36 pm

I haven't checked the BIOS voltage monitoring but IMO nothing beats a calibrated multimeter. I'll look to see how it is when I get home.

I did have a multimeter that went bad a while ago... it was reading about a voltage off and i couldn't calibrate it.

I'm also going to try downgrading catalyst to 12.8. Noticed some other forum posts in other sites saying they have some issues with 13.1. maybe its just a software issue and not a voltage issue.
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Re: How low is too low on 12V rail?

Postposted on Tue Apr 30, 2013 9:10 am

looks like downgrading to 12.8 worked. left games running for 6 hours while mining without a single crash. I guess my idea about voltages and temperatures were just way off the mark.
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