Running a 832W system on an 850W PSU?

[druppes]

How bad is it to run a PC very close to the PSU limit?

So i'm swapping all my old parts into a new case and adding some new parts.

The full system load seems to be around 830W based on online power supply calculators with some hefty overclocks on everything.

Is it really a problem to be running so close to its maximum wattage?

The full system is:

EVGA 152-HR-E979-KR - EATX
4790k @4.9ghz (water-cooled)
2x GTX 780 overclocked slightly. (water-cooled)
GSkill Ram 32GB @ 2400mhz DDR3 (water-cooled)
DDC 3.2 Pump 18v
PCI raid controller (not bought yet)
8x 3GB 3.5" WD red raid 10
4x 500gb SSD raid 0
1 x 2tb 2.5" sed backup

I'm thinking my options are:

keep PSU see if it works. (is this safe?)

keep PSU and buy a molex PSU to run all the Hdds and pump from

New 1000W or 1200W PSU (obviously if I could afford this I would do this without question but its a massive push for me)

Thanks for any suggestions!!

 

[turkey3_scratch]

Labelled wattage does not matter, what does matter is the quality of the PSU and how well it tests by professional reviewers.

You listed everything but your power supply...

 

[Math Geek]

you are not at 800+ watts. those calculaters are normally way off. add up some numbers. the 780 is about 250w each so 500w. a 4790k is 88w, maybe 110 or so highly overclocked, heck call it 125w just to be overly safe.

you're at 625w which is a high esimate. the rest of the parts may add another 100w. so a high guess is about 725w which is about 85% of the capacity of the psu. this is in the safe usage zone for a quality unit. that's the magic piece that is missing. what psu model is it? if it a junk unit, then an upgrade would be worth it. if it is quality already, then you can stay where you are at.

so what psu do you have now?

 

[druppes]

Haha yeah would have been helpful to link my PSU .

850W Silverstone Strider, Full Modular, 80PLUS Gold,

No idea if its decent or not.

 

[Mr5oh]

you are not at 800+ watts. those calculaters are normally way off. add up some numbers. the 780 is about 250w each so 500w. a 4790k is 88w, maybe 110 or so highly overclocked, heck call it 125w just to be overly safe.

you're at 625w which is a high esimate. the rest of the parts may add another 100w. so a high guess is about 725w which is about 85% of the capacity of the psu. this is in the safe usage zone for a quality unit. that's the magic piece that is missing. what psu model is it? if it a junk unit, then an upgrade would be worth it. if it is quality already, then you can stay where you are at.

so what psu do you have now?

This right here. And the odds of you fully loading everything at the same time is not very likely, especially for extended periods. So as mentioned, you need to tell us what PSU you have.

 

[Math Geek]

you should be ok with that psu. it is pretty good quality. here is johny's review of it if you wish to read it http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story6&reid=365

knowing you'll stay below 700w even at high loads, i'd have no concerns using the psu for the system.

 

[turkey3_scratch]

you are not at 800+ watts. those calculaters are normally way off. add up some numbers. the 780 is about 250w each so 500w. a 4790k is 88w, maybe 110 or so highly overclocked, heck call it 125w just to be overly safe.

you're at 625w which is a high esimate. the rest of the parts may add another 100w. so a high guess is about 725w which is about 85% of the capacity of the psu. this is in the safe usage zone for a quality unit. that's the magic piece that is missing. what psu model is it? if it a junk unit, then an upgrade would be worth it. if it is quality already, then you can stay where you are at.

so what psu do you have now?

This right here. And the odds of you fully loading everything at the same time is not very likely, especially for extended periods. So as mentioned, you need to tell us what PSU you have.

I think it's always smart to have a PSU prepared for the worst of situations. It's a bad peace of mind knowing that if under a specific stressful condition, your PSU may not handle the load.

 

[Math Geek]

me too, that's why all the numbers are over estimates. 😀 i'm sure a torture test could cause it to spike but i still doubt that would even get to these high numbers. are you suggesting a higher wattage?

i have never used this gpu so if you know some numbers i don't then please correct me. for all i know a small oc may just add a lot to the power usage. i did not look up spefici benchmark numbers only looked at oem tdp listing.

 

[photonboy]

http://www.guru3d.com/articles-pages/geforce-gtx-780-sli-review,4.html

440W.
Obviously that's too low due to his various drives and i7 overclock but even if we add 160W that's still only 600W with some more leeway for worst-case load scenarios.

It's not high enough that I'd look closer to see if his PSU will have any issues. I see no indication of power problems.

 

[druppes]

Awesome thanks guys, i'm feeling much more relaxed about everything now!

 

[turkey3_scratch]

No I'm not suggesting a higher unit. It's just that looking at the Tomshardware review for the reference 780, it is spot-on with what you said, 250W under stress test. The only thing I'm wondering is how much his GPU is overclocked. Let's say his GPU is overclocked to merit 300W, which is totally realistic. Then you got 600W for the GPUs. CPU at 4.9Ghz will use a good amount of power, probably 140-150W. It also sounds like he has a custom water cooling loop, I think his loop could use somewhere near 50W IMO. Plus the rest of the system, I'd say 850W is almost spot-on with what his rig may actually consume. Jonnyguru's hot test only puts 774W of loas on the 12V rail.

I don't know, it should be fine though. As said, it's be extremely rare for this type of load, and I think it'll handle it fine. Yeah I think he's fine and I am probably overestimating a bit.

 

[photonboy]

i7 overclock:
A lot of people don't do this quite right.

If the multipliers are set different per core load then you drop as core load rises. For example:
4.9-> 1 core
4.8-> 2 core
4.7-> 3 core
4.6-> 4 core

The best way to check is run Prime95 and monitor the Task Manager. Look to see if CPU performance is closer to 4.9GHz (or slightly lower) or closer to 4.6GHz (or slightly lower).

If you drop the top frequency/voltage and raise the multipliers you might see something more like:

4.7GHz - 1 core
4.7GHz - 2 core
4.6GHz - 3 core
4.6GHz - 4 core

I don't have Haswell so perhaps that's not applicable but I think it still is.

Anyway, it's possible to run COOLER and/or have the same or better performance if you tweak carefully.

(It can make a big difference to the heat output depending on the setup)

 

[turkey3_scratch]

Well, I sort of agree with you tea urchin. If Hardwaresecrets had done the said review above, I'd feel a lot safer since Gabriel overloads the units and sees where the protections kick in and what not. Plus if you take into consideration derating, that also decreases its capabilities. But really it depends on the unit itself, and I'm not altogether sure if the Jonnyguru review is suited for making these situations where things get so close. And as I said, it depends on the GPU overclocks, that is a huge factor.

I know I keep changing my mind, but I think he might be better off with a new unit.

 

[photonboy]

The strider is a great unit.
The problem with math geeks first answer is he points out its about 85% of the power supply absolute maximum limit.(as a high estimate)
85% Is not a 'safe zone' unless you do not mind the unit lasting months , not years.
The next problem is the power supply maximum wattage (850) is across all voltage rails, whilst your stated load will be mainly on the 12 volt rail.(700/what ever)
This will push the % of maximum even higher on that rail to the point of no headroom.
Inductive start up loads etc even with a strider unit will drag its life expectancy down.
This is why there is usually a 100 watt discrepancy in cross fire/ sli configuration power recommendations.
It is to keep the % headroom you are not really aware of with a single card.

http://silverstonetek.com/legacy.php?area=en&model=ST85F-G&tno=2
1) 950W peak
2) 840W for the 12V rail
3) 440W for basic 2xGTX780 system
4) 600W approx may be his maximum load with overclock, drives etc, perhaps spikes up to 700W but I'd be surprised

*I MADE A MISTAKE**

The "440W" is apparently just for the two 780's not the system. Sorry about that. That does make it a bit more of a problem.

Another site says just over 400W for overclocking a single 780 so apparently add another 230W + 100W for CPU overclock/other and we're estimaging:
730W?

So, sorry, yeah I agree that's probably pushing it too close.

 

[turkey3_scratch]

I disagree with the 440W for 2X GTX 780. Under gaming load, that is realistic, but shouldn't we take stress test load into consideration? Games like AC Unity really do incude these kinds of stress test loads, so there are some real-world applications where a GTX 780 will be taxed quite farther than 220W, moreso with an overclock.

 

[druppes]

No I'm not suggesting a higher unit. It's just that looking at the Tomshardware review for the reference 780, it is spot-on with what you said, 250W under stress test. The only thing I'm wondering is how much his GPU is overclocked. Let's say his GPU is overclocked to merit 300W, which is totally realistic. Then you got 600W for the GPUs. CPU at 4.9Ghz will use a good amount of power, probably 140-150W. It also sounds like he has a custom water cooling loop, I think his loop could use somewhere near 50W IMO. Plus the rest of the system, I'd say 850W is almost spot-on with what his rig may actually consume. Jonnyguru's hot test only puts 774W of loas on the 12V rail.

I don't know, it should be fine though. As said, it's be extremely rare for this type of load, and I think it'll handle it fine. Yeah I think he's fine and I am probably overestimating a bit.

Thanks,

The loop uses 18W under full load and 10W under normal. I plan on having 12 120mm fans and 1 140mm fan all running very slowly. i'm estimating about 25W for the lot. As for the HDDs thats where I started to worry as I think they use around 5-6W each, which means about 50W. (ssd I think take about 0.5-1W each)

95W for fans, loop and Hdds.

280W per GPU to be on the safe side with a mild overclock.

140W CPU

30W for lights mobo etc.

Its 825W. Is this still okay? I use the PC for video editing which will run the CPU on 100% on all cores and 1 GPU on 100% and the other on about 40%. This can be like this for over 5 hours at a time and on rare occasions over 30 hours at a time. However even with my old setup where I had plenty of space I often switched to my lower clock speeds for lengthy video transcoding to help the system be more stable and cool.

 

[turkey3_scratch]

That is with a base 863MHz frequency. Anandtech overclocked the GTX 780 reference to 1063Mhz. Anandtech said this was a 55W increase from the wall, so assuming 80% efficiency, so another 44W. So more like 290W.

 

[turkey3_scratch]

Yeah, I did overestimate before. I think you're good 😉

 

[photonboy]

I disagree with the 440W for 2X GTX 780. Under gaming load, that is realistic, but shouldn't we take stress test load into consideration? Games like AC Unity really do incude these kinds of stress test loads, so there are some real-world applications where a GTX 780 will be taxed quite farther than 220W, moreso with an overclock.

See my updated comment. My new estimate for his system is about 730W.

 

[turkey3_scratch]

Wait, so now you say you think it's not fine, right after I said I think it's fine? 😛 I gotta quit changing my mind.

My new thing is that we don't know enough about the PSU to be able to determine how it will run or not. As I said, Jonnyguru does not test everything, they don't have the resources some other places do, so we don't know when the protections kick in, or how the voltages are when the PSU is overloaded. If we knew those two things, we could easily figure out if this was sufficient or not.

 

[druppes]

Slightly confused if everyone is suggesting a new unit or to give this one a try. I'm not too fussed about the PSU itself giving up so long as my other components are safe. Also thinking about it. The Hdds will never all be running at the same time as i'm likely to have separate sets of raid etc.

 

[turkey3_scratch]

Slightly confused if everyone is suggesting a new unit or to give this one a try. I'm not too fussed about the PSU itself giving up so long as my other components are safe. Also thinking about it. The Hdds will never all be running at the same time as i'm likely to have separate sets of raid etc.

I would be confused if I were you, too. We're like a bunch of chickens running in circles yelling out different things :lol:

 

[druppes]

Haha Also another option is that I have room for a second ATX PSU but Iv been avoiding that as I'm not sure how to get it to turn on with the other one etc. And how to properly install it etc. I guess the idea would be to power one of the GPUS with a 400W cheap but solid PSU.

 

[photonboy]

Those cards fetch so much money on feEbay, I would sell them both separately and buy a gtx 980.t.i.
This would cost a smidge more than a new power supply but you wouldnt end up with a perfectly good gold rated psu swinging in the wind.

Worth considering if the price is right, though at this point I'd probably wait for one of the new GPU's.

Also...
Maybe someone said this, but i wouldn't put all those hard drives in the same computer. Every time he turns the PC on or does certain things all EIGHT of his hard drives start up.

I'd get a NAS instead and put most or all of them in it, and have a Gigabit switch connecting them via ethernet if he really needs the fast access. A good PCI raid controller costs a bit of money, so he can just forget that and put the cost toward a NAS.

I have a WD MY CLOUD device. My Gigabit Switch connect to the Router, my PC, and the WD MY CLOUD. When I access it that goes directly through the Gigabit Switch so the router is not in the loop. Thus, my access speed is whatever the device is routed for (up to about 120MB/second which may be slower than what you get for sustained access now but it's a tradeoff I'd certainly make, plus you have SSD's which I assume you use for any of the stuff you need fast access to.)