maxed out PSU

[Morbid]

hi. i got a question in regards to a rig i built (https://bitcointalk.org/index.php?topic=7216.msg2602216#msg2602216). im running at 240V, when at stock clocks the total current off the wall was 5A (1200W). then if i downclock it goes down to 4.7A (1130W). Overclocked peaked at 5.5A (1320W). i have corsair AX1200 which is able to handle more than 1200W as peak though could someone please advise whether running at full load will dramatically reduce its lifetime. i plan on using it for at least two years. thanks.

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[tom_o]

hi. i got a question in regards to a rig i built (https://bitcointalk.org/index.php?topic=7216.msg2602216#msg2602216). im running at 240V, when at stock clocks the total current off the wall was 5A (1200W). then if i downclock it goes down to 4.7A (1130W). Overclocked peaked at 5.5A (1320W). i have corsair AX1200 which is able to handle more than 1200W as peak though could someone please advise whether running at full load will dramatically reduce its lifetime. i plan on using it for at least two years. thanks.

Maybe try undervolting the cards, since doing this should reduce the power draw quite a lot. Also each of those 120mm fans probably draws at least 10-12w so powering them separately should give you another 60-72w headroom.

Also the power drawn from the wall isn't exactly what the PSU is outputting - you have to think about the PSU inefficiencies too.

And disabling one core of the CPU in BIOS will cut some power consumption too.

[Morbid]

hi. i got a question in regards to a rig i built (https://bitcointalk.org/index.php?topic=7216.msg2602216#msg2602216). im running at 240V, when at stock clocks the total current off the wall was 5A (1200W). then if i downclock it goes down to 4.7A (1130W). Overclocked peaked at 5.5A (1320W). i have corsair AX1200 which is able to handle more than 1200W as peak though could someone please advise whether running at full load will dramatically reduce its lifetime. i plan on using it for at least two years. thanks.

Maybe try undervolting the cards, since doing this should reduce the power draw quite a lot. Also each of those 120mm fans probably draws at least 10-12w so powering them separately should give you another 60-72w headroom.

Also the power drawn from the wall isn't exactly what the PSU is outputting - you have to think about the PSU inefficiencies too.

And disabling one core of the CPU in BIOS will cut some power consumption too.

i might be a knob since never had to use so much current before. so this psu is stated to give 1200W, meaning it is designed to consume 1350W off the wall? - taking into account its 87% efficient.

[redtwitz]

At 87% efficiency, if the PSU delivers 1200 W, it will consume 1200 / 0.87 = 1380 W.

If it's currently drawing 1200 W from the wall, it's delivering 1200 * 0.87 = 1044 W (again assuming 87% efficiency).

[Morbid]

At 87% efficiency, if the PSU delivers 1200 W, it will consume 1200 / 0.87 = 1380 W.

If it's currently drawing 1200 W from the wall, it's delivering 1200 * 0.87 = 1044 W (again assuming 87% efficiency).

+1 thanks. will try to find optimal power draw tomorrow.

[Trillium]

Also the power drawn from the wall isn't exactly what the PSU is outputting - you have to think about the PSU inefficiencies too.

To make it worse, PSU conversion efficiency does not vary linearly with load.


OP Should look at underclocking memory speeds to save on power too (and reduce card temps), assuming he's mining SHA-256 coins. (Don't underclock if running scrypt, usually).

[suprabitz]

you shouldnt run your psu at 100%. keep in mind when gaming you may run at 100%+ for a couple hours then your computer is idling or off for most of the day so your PSU has cool down time before cycles. it takes time for wires to overheat so couple hours at 100% is not a big deal.

in mining your computer is pegged at 100%. if wire temps creep up slowly you could end up overheating especially with poor ventilation

for example go buy a new car and run it at redline on a dyno for 24/7 and see how long it lasts.

these are not industrial power supplies they are consumer PSUs they are not made for that abuse. it certainly won't last years.

also if you look at the efficiency charts the highest efficiency is usually 80-85% of max output. You lose efficiency when running it close to the limit so you're flushing profits away.

[crazyates]

At 87% efficiency, if the PSU delivers 1200 W, it will consume 1200 / 0.87 = 1380 W.

If it's currently drawing 1200 W from the wall, it's delivering 1200 * 0.87 = 1044 W (again assuming 87% efficiency).

+1 thanks. will try to find optimal power draw tomorrow.

To make it worse, PSU conversion efficiency does not vary linearly with load.

The 80Plus Gold spec specifies a MINIMUM of 88% efficiency when under 100% load on a 230V line. Source. So you're most likely at 88-89%.

My rule of thumb is to draw at the wall what the card is rated for. So if you've got a 1200W PSU that's pulling 1200W from the wall, you're prolly good.

[Gomeler]

I have 2 AX1200s that I ran at 1150-1250w from the wall for 9 months with ambient temps around 25-35 Celsius. Zero problems. I'm reassembling those rigs right now after replacing failing/aging components and plan on pulling the same wattage for another ~9 months with zero concerns about the PSUs. My HD 5970s died long before the PSU quit on them.

[Morbid]

i have a quick update. basically i been tinkering about with this for couple of hours & i think i got it to give me the highest hash/s for stock voltages (voltage locked cards dammit!) here is my idle current off the wall:


and here is few minutes into the full load overclocked to 1000/6000:


basically i got 5.3A x 240V = 1272W * 0.88 = 1120W. so judging by your experience i conclude that it will be ok for 24/7. thank you guys for your advice!

[Trillium]

Wait, are you measuring 1200+ watts through your multimeter? 

[Morbid]

Wait, are you measuring 1200+ watts through your multimeter? 

why not? it takes upto 10A. through connector block.

[Trillium]

Usually the leads aren't rated for it. I guess that's a quality multimeter for real mains testing then (ie. not <$100 hobbyist type). I've melted cheap ones with as little as 100 watts.

[Morbid]

Usually the leads aren't rated for it. I guess that's a quality multimeter for real mains testing then (ie. not <$100 hobbyist type). I've melted cheap ones with as little as 100 watts.

its above average meter with thickish multistrand silicon leads. usually sells for ~ 1BTC .

[fractalbc]

The multimeter leads are probably 18AWG so are good for 7-13 amps (in conduit - open air) so are fine for measuring 5 amps.  I wouldn't leave it hooked up that way long term but those leads are perfectly safe at meter maximum reading of 10 amps.

You are at the limit of what that supply can provide.  You are probably drawing almost all of your power from the +12v rail and that PSU is rated at 12V 100A.  I don't like designing systems that run over 80% and you are exceeding that.  But, it is likely to work for a while at least.