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Message boards : Graphics cards (GPUs) : 600W PSU for 2 GPU System

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Stephen Farrell
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Message 42755 - Posted: 5 Feb 2016 | 14:44:58 UTC

Hi,

I have been running 2 GTX750Ti cards for GPU grid on my system with a 600W PSU for a while now and decided to upgrade one of the cards to a GTX970. Both seem to be running happily with the current PSU.

Although this is the case I was wondering whether or not this will be safe in the long run as the GTX970 has a considerably higher power draw that the 750's.

The PSU is a Corsair CX600.

Stephen

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Message 42756 - Posted: 5 Feb 2016 | 16:23:12 UTC - in response to Message 42755.
Last modified: 5 Feb 2016 | 16:32:14 UTC

145W TDP for the GTX970 + 60W TDP for the GTX750Ti is 205W.
Your CPU has a stock TDP of 125W and it's reasonable to expect it would use close to that if you use it to crunch.
Other system components typically use ~50W, so your system is likely using around about 380W if you run at stock/reference values.

That Corsair (CX600) is good for up to 480W on it's main 12V rail. Your disks will probably come off the 3.3V and 5V rail.

The PSU has a MTBF (Mean Time Before Failure) of 100Khours (11years) and comes with a 2year RTM warranty.

It's a Bronze level 'Builder Series' model, and it would in my opinion be reasonable to expect it to do the job, however I tend to use higher end models of PSU as they are more reliable and more power efficient (and more cost efficient for me in the long run).

If you are thinking of upgrading (say because you've had the PSU for 2years) the RM series are great value for money. Even at 115V you would get close to 90% power efficiency using 380W on an RM750i and the RM series warranty is longer 5 or 7 years.

Most PSU's are efficiency optimized for ~50% usage.
There are other good PSU manufacturers (but not many)!
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Stephen Farrell
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Message 42757 - Posted: 5 Feb 2016 | 16:57:18 UTC - in response to Message 42756.

Hi,

Thanks for the advice. I'm due a new psu and plan to replace the second 750 soon so will look at the RM.

Much appreciated.

Stephen.

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Message 42761 - Posted: 6 Feb 2016 | 12:53:35 UTC - in response to Message 42757.

Hi,

Thanks for the advice. I'm due a new psu and plan to replace the second 750 soon so will look at the RM.

Much appreciated.

Stephen.


On other thing to consider is that the 'better' the rating, ie Bronze, Gold or Platinum, the cooler the psu runs to due to it being more efficient in it's operations. The cost goes up too, but it gets quite warm, low 90's despite being in the 30'sF outside, in my basement because I went cheap and bought Bronze level or lower psu's. I have 11 pc's in my basement. As I replace them I do get the better ones and only buy 750 or 850 watt psu's so in theory they aren't running flat out like my cpu's and gpu's are. Hopefully this will make my investment pay off by them lasting much longer.

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Message 42774 - Posted: 8 Feb 2016 | 0:49:21 UTC

skgiven is spot on with his math. You should always work out how much you are drawing from each rail with multi GPU systems.

One quick sanity check is whether you have enough plugs on your power supply for your equipment. Your CX600 has two which is the right number to run your GTX970. Most 750TI's don't need any. There are a few overclocked models that do but most do not. So, the sanity check passes and the math works out. Your system should be fine with the CX600 as it is.

FWIW, my dual 750ti system draws 144 watts from the wall with an ungraded 80+ rated 380 watt supply. That makes it around 115 watts for the mostly idle CPU and two 750Ti's crunching GPUGRID assuming an 80% efficient supply.

I budgeted 200 watts each for factory overclocked GTX970's to be safe in my build. The Nvidia control panel says my GTX970 is currently drawing 154 watts with a cap of 201 on a GERARD_CXCL12 work unit. I only have one card so far but built the system to take two. A pair will use up to 400 watts. Add another 200 for the rest of your system and you are looking for a power supply of at least 750 watts with 4 PCIe power plugs to run at 80% load. The supply proposed by skgiven is a decent choice. I might look at a slightly bigger supply to give a bit more headroom for your higher power CPU as I prefer to aim for 60% load on more modest systems. It is tough to get a power supply with enough PCIe plugs to run a pair of GTX970's rated less than 750 watts but they do make them so the sanity check alone is not enough.

I rarely recommend the higher 80+ ratings below 600 watts. They will never pay for the extra purchase price in saved electricity. You are at the point that you should consider a higher rating (gold / platinum ) if you can get one at a good price. You might make back 20 dollars. You probably won't make back 50.

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Message 42791 - Posted: 10 Feb 2016 | 10:05:00 UTC - in response to Message 42774.

Hey, thanks for the reply. I went for the corsair 850i platinum series to give myself room for future upgrades. I found that the 970 is a vast improvement on the 750Ti and decided to just go ahead and get another. Just waiting for delivery of that atm. Unfortunately I couldn't stretch to the 980 just yet.

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Message boards : Graphics cards (GPUs) : 600W PSU for 2 GPU System