# Is my 1000W power supply too small?



## The Von Matrices (May 4, 2013)

Hi everyone,

I just bought and installed a 3rd HD 7970 in my system (primarily for bitcoin mining, but also for games).  I am now surprised to find out that my system is unstable.  At first I assumed that my CPU overclock was affecting something with the new card, so I put the CPU back to stock settings.  The system is stable now, but I don't think the CPU overclock was directly at fault.

I plugged the system into my Kill-A-Watt meter, and the tower is drawing 1050W mining on the three cards (with CPU at stock settings and lightly loaded).  I know the PSU has some conversion inefficiency, but this means it's at about 95% capacity, right?  I bought my 1000W power supply three years ago and I supposedly thought it would be the last power supply I would ever need.  But now I wonder if I need to get a larger power supply if I want to reinstate the CPU overclock.  I'm just surprised that this situation came up and I want to make sure that I am on the right track before I put down the money to buy a larger supply.  Does my system power draw make sense?

I was considering the Seasonic X-1250 due to its stellar voltage regulation (voltage drops are very common where I live).  I do not plan to add any more video cards or hard drives, just reinstate the CPU overclock.  Do you think 1250W will be enough?

Thanks for the advice in advance.


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## Sinzia (May 4, 2013)

I used my AX1200 with 3 overclocked GTX480's and a heavy overclocked 2600k and it was reading ~1000 watts on my UPS.

The 1250 might not be enough with all the overclocking.

There's also a few adapters you can use to add a second PSU to a system, one being http://www.add2psu.com/


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## Anarchy0110 (May 4, 2013)

I think you can get a 1500W one like the Silverstone Strider  Just to be safety enough


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## Jack1n (May 4, 2013)

Three 7970's consume about 600-700w at full load,which leaves AT LEAST 250w for the rest of your system which i believe to be enough.


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## Aquinus (May 4, 2013)

Jack1n said:


> Three 7970's consume about 600-700w at full load,which leaves AT LEAST 250w for the rest of your system which i believe to be enough.



For two overclocked Westmere Xeons? Haha, really funny. My 3820 overclocked right now while crunching on all cores has me running at 350-watts loaded without any load on the GPUs and one of them fully powered down.

Overclocking the bclk might cause it to become unstable. It depends on how stable the connection is between BOTH CPUs and the IOH. If QPI is clocked too high you could be causing the IOH to become unstable when it starts moving a lot of data. It's just a guess, but you definitely should consider a bigger PSU.


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## Jack1n (May 4, 2013)

Aquinus said:


> For two overclocked Westmere Xeons? Haha, really funny. My 3820 overclocked right now while crunching on all cores has me running at 350-watts loaded without any load on the GPUs and one of them fully powered down.
> 
> Overclocking the bclk might cause it to become unstable. It depends on how stable the connection is between BOTH CPUs and the IOH. If QPI is clocked too high you could be causing the IOH to become unstable when it starts moving a lot of data. It's just a guess, but you definitely should consider a bigger PSU.



Two? his system specs only state one.


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## Aquinus (May 4, 2013)

Jack1n said:


> Two? his system specs only state one.



Ah, I misread it. You're right, should be enough, but barely. He even said himself that he's drawing about 1000w with the 7970s loaded and light load on the CPU though. I'm still leaning towards the QPI link being clocked too high reason if setting everything to stock fixed it.


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## Jack1n (May 4, 2013)

Aquinus said:


> Ah, I misread it. You're right, should be enough, but barely. He even said himself that he's drawing about 1000w with the 7970s loaded and light load on the CPU though. I'm still leaning towards the QPI link being clocked too high reason if setting everything to stock fixed it.



But thats the wierd part about it,if he is bitcoin mining his CPU should bearly be under any load,even a custom 7970 with 2x8pin can only physically draw 275w ech which means 825w power draw from the gpus in total in an extreme circumstance.


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## McSteel (May 4, 2013)

The HX1000 is only around 82% efficient at those load levels, so ~1050W from the wall means the PSU is delivering around 860W. You're still good. I don't think you need to change your PSU.


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## The Von Matrices (May 5, 2013)

Jack1n said:


> But thats the wierd part about it,if he is bitcoin mining his CPU should bearly be under any load,even a custom 7970 with 2x8pin can only physically draw 275w ech which means 825w power draw from the gpus in total in an extreme circumstance.





Jack1n said:


> Three 7970's consume about 600-700w at full load,which leaves AT LEAST 250w for the rest of your system which i believe to be enough.



That's true, but I do have them overclocked to 1125MHz core, so that would account for some more power.  I would think that would add another 100-150W total to the system.  This would leave 150-200W for the entire rest of the system - CPU, memory, motherboard, drives, and cooling.  I don't think it's unreasonable that with a CPU overclock I would hit over 1000W.



McSteel said:


> The HX1000 is only around 82% efficient at those load levels, so ~1050W from the wall means the PSU is delivering around 860W. You're still good. I don't think you need to change your PSU.



Wow, I didn't realize that my power supply was that inefficient.  I'm looking at the Enermax Maxrevo 1500W and that gets 92% efficiency at 50% load.  That's pretty significant.  If I'm saving 100W mining that could sum to a significant amount of money over time.


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## radrok (May 5, 2013)

The Von Matrices said:


> Wow, I didn't realize that my power supply was that inefficient. I'm looking at the Enermax Maxrevo 1500W and that gets 92% efficiency at 50% load. That's pretty significant. If I'm saving 100W mining that could sum to a significant amount of money over time.



That's a very solid choice

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story6&reid=302


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## Elfear (May 5, 2013)

You might consider downclocking and undervolting your cards. With a 2600k at stock clocks and three 7970's at 1050/340 (1.05V), my system draw at the wall is ~640W while mining. With four 7970's at the same clocks total power draw is 840W. 

Decreasing clocks will lower your hash rate a little (mine is ~630Mhash/sec per card) but your power draw will go down significantly.


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## GamerGuy (May 5, 2013)

Sinzia said:


> I used my AX1200 with 3 overclocked GTX480's and a heavy overclocked 2600k and it was reading ~1000 watts on my UPS.
> 
> The 1250 might not be enough with all the overclocking.


Not true, I have a 3960X @4.5ghz, 3x HD7970 @1080/1425, plus a H100 + 2x 120mm Corsair SP fan, an SSD + 3x WDC Black with 2x 200mm + 140mm case fans, and they're running off an X-1250. I had a HX1050 running this exact setup a while back, and though it was coping with it, the air vented from the back of the PSU seemed a tad warmer than I was comfortable with, so I swapped out the HX1050 in favor of the X-1250 and it's been great since.


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## OneMoar (May 5, 2013)

90% efficiency try more like 75% in most cases (temperature,workload,input power "cleanness") all have a effect   with 3 7970's it would not surprise me if you are overtaxing a KW psu 
the problem here is is that you are gonna start throwing the breakers once you get beyond 1200 or so


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## The Von Matrices (May 5, 2013)

OneMoar said:


> 90% efficiency try more like 75% in most cases (temperature,workload,input power "cleanness") all have a effect   with 3 7970's it would not surprise me if you are overtaxing a KW psu
> the problem here is is that you are gonna start throwing the breakers once you get beyond 1200 or so



Thanks for the advice.  I have had that problem in the past and actually changed the wiring in my house because of breakers tripping.  I used to have more devices on the circuit with my PC but my GTX 470 SLI system could cause the breaker to trip when my brother also had the plasma TV on at the same time.  I changed the circuit so that now the 15A breaker only powers two table lamps and the computer, so unless the system is drawing ~1800W, it should not cause a problem.


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## Sinzia (May 5, 2013)

GamerGuy said:


> Not true, I have a 3960X @4.5ghz, 3x HD7970 @1080/1425, plus a H100 + 2x 120mm Corsair SP fan, an SSD + 3x WDC Black with 2x 200mm + 140mm case fans, and they're running off an X-1250. I had a HX1050 running this exact setup a while back, and though it was coping with it, the air vented from the back of the PSU seemed a tad warmer than I was comfortable with, so I swapped out the HX1050 in favor of the X-1250 and it's been great since.



Different systems with different components and different overclocks. What I said was factual.


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## The Von Matrices (May 5, 2013)

Elfear said:


> You might consider downclocking and undervolting your cards. With a 2600k at stock clocks and three 7970's at 1050/340 (1.05V), my system draw at the wall is ~640W while mining. With four 7970's at the same clocks total power draw is 840W.
> 
> Decreasing clocks will lower your hash rate a little (mine is ~630Mhash/sec per card) but your power draw will go down significantly.



That's a good idea, but there's a few things that are working in favor of overclocking for me right now.  Electricity where I live is very cheap ($0.077/kWh) and since the temperatures are still cold outside I don't have to use air conditioning (or heating).  So the extra hashes are still profitable even if my system is not running at peak efficiency.  Once summer temperatures come and I have to use air conditioning, then I probably will put the cards back to stock speeds.  At some point in the next few months though I anticipate that ASICs will make the difficulty go up so much that GPU mining won't be profitable and then I will just shut off mining and only use the GPUs for games.  I still will probably have the GPU's overclocked for the games though so the PSU's extra capacity won't go to waste.


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## drdeathx (May 5, 2013)

Jack1n said:


> Three 7970's consume about 600-700w at full load,which leaves AT LEAST 250w for the rest of your system which i believe to be enough.



An overclocked 3770K with 3 x 7970's overclocked pull over 1000 watts at full load.I also tested it. 2 x 7970's drew about 740 watts with a 3770K overclocked at full load.


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## GamerGuy (May 5, 2013)

Sinzia said:


> Different systems with different components and different overclocks. What I said was factual.


That's just your opinion, anecdotal at best, not fact. Fact is, many people are running TriFire HD7970 with AX1200 and higher. It is more than sufficient for three HD7970 and whatever other system configuration you may have, for QuadFire, then I'd say it won't be sufficient. Here's a Kitguru review of the TriFire HD7970, they have their i7 970 @4.6ghz + 3x HD7970 with a Corsair AX1200:
http://www.kitguru.net/components/graphic-cards/zardon/asus-hd7970-tri-crossfire-review/4/

My main system has an X3960 @4.5ghz, three OC'ed HD7970's, AIO WC, HDD's and fans....not a single power related issue.


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## Frick (May 5, 2013)

OneMoar said:


> the problem here is is that you are gonna start throwing the breakers once you get beyond 1200 or so



No you wouldn't. Oh yeahhhh you americans and your weak electricity.


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## Aquinus (May 5, 2013)

Frick said:


> No you wouldn't. Oh yeahhhh you americans and your weak electricity.



Huh? I have 208v 70 Amp split-phase coming into my apartment and the room I'm in has a 20A 115v breaker. It's actually pretty funny because when a transformer down the street popped the fuse on the power line, half of my apartment had power because the other transformer on the other half of that split-phase connection was still active and come to find out half of my apartment is wired to one phase, the other half to another, and the 208v ports provide two hot outputs.

Then I can go over to the house where I grew up in, where I don't remember the amperage ratings on the fuse box, but I do recall that I had access to three-phase power off the street.


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## Frick (May 5, 2013)

Aquinus said:


> Huh? I have 208v 70 Amp split-phase coming into my apartment and the room I'm in has a 20A 115v breaker. It's actually pretty funny because when a transformer down the street popped the fuse on the power line, half of my apartment had power because the other transformer on the other half of that split-phase connection was still active and come to find out half of my apartment is wired to one phase, the other half to another, and the 208v ports provide two hot outputs.
> 
> Then I can go over to the house where I grew up in, where I don't remember the amperage ratings on the fuse box, but I do recall that I had access to three-phase power off the street.



I've heard a lot of americans with just 115V 15A breakers.


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## Aquinus (May 5, 2013)

Frick said:


> I've heard a lot of americans with just 115V 15A breakers.



The smaller rooms in my apartment are on 15a, but not this room. I also have a 50a 208v breaker. Not quite sure what they intended that to be used for since there aren't any hookups for a washer/dryer. I have two spots for ACs that have independent 20a 208v as well.


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## OneMoar (May 5, 2013)

Aquinus said:


> The smaller rooms in my apartment are on 15a, but not this room. I also have a 50a 208v breaker. Not quite sure what they intended that to be used for since there aren't any hookups for a washer/dryer. I have two spots for ACs that have independent 20a 208v as well.



15Amp is is what everyone uses overhere with some people having 20AMP


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## blibba (May 5, 2013)

Two questions:
-Is your system unstable only with Furmark+Prime95, or in general use? Because as someone else mentioned, Bitcoin mining won't load your CPU, and games won't draw the full TDP of your cards.
-Do you know from your power-meter the difference in power consumption on your CPU between overclocked and stock? Then, using the efficiency stats, we could work out whether you're over capacity. If you're not, slightly nudging up the voltages might actually fix the problem by compensating for the slightly deteriorated voltage regulation at very high output.


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