Computer Shuts down under load.

[kwelz]

So I just rebuilt my PC using a Maximus V Formula board with a 3570K and 2x 680s. Today I was trying to run a benchmark (3dMark 11) and when it got most of the way through the computer shuts down. I am unable to restart the computer without letting it set for a few minutes. In addition the start button built onto the board is dim and flickering.

At first I thought it may be a thermal issue however my temps are staying well within norm. So I went to troubleshooting. I set bios back to default. No overclocking, etc. Same results. I finally removed my second video card and the problem went away. So it seems like it is a power issue. Power supply is an OCZ ZT 750 so it should be more than sufficient to power this system.

Here is the final interesting thing. This I never had trouble running this benchmark before. the only things that have changed is that I switch the board from a P8Z77-V pro to the Formula and used the MPCIE car to install a 120gb SSD for my OS.

Thoughts? I have to be missing something here.

[Myk_SilentShado]

if you had a 850W, I would say you're probably pushing it, but no; a 750W is not enough for 2 680's.

[kwelz]

It was never an issue before. Seriously. The computer ran with the old board, same Power supply and same vid cards till this week and never had a single issue. That is why I am so perplexed. I could not see the board making a big difference. When I looked at the numbers I figured I needed about 675 Watts. The 750 gave me a margin of error I thought.

[Myk_SilentShado]

Yeah, but you have to consider 2 things:
1. Your margin for error only leaves you with 75W for the rest of your hardware...less if you're overclocking
2. You're constantly running your PSU at 90% of it's capacity. If your PSU is rated for 80% efficiency, you're slowly killing it.

Plus, the dimming/flickering start button is a clear indicator you don't have enough power.

[kwelz]

Well I am just an idiot I guess. For some reason it really didn't occur to me that running it that close to the line would be a problem.
In the short term I guess I need to pull one of the cards.

Now another question if you will. I have been tinkering with the idea of replacing the two cards with a 780Ti. If I do decide to go this route would the 750 be ok. Or should I just consider replacing it regardless at this point?

Thanks!

[Myk_SilentShado]

You should be fine to run a 780 ti from the 750W, your PSU is rated at 85% capacity which is 637.5W and the 780ti consumes at most 375W, leaving you just under 263W of room, but, if I were you. i'd take that PSU to someone who can test it and make sure it hasn't suffered too much.

[kwelz]

I think I may just play it safe. Move the 750 to my Media PC I am building since it is low power and then Pick up a new higher rates one just in case for this computet

[Myk_SilentShado]

That's a good idea, I recommend a 850W minimum PSU. Silverstone or Seasonic are the 2 top picks. If you can afford it, get one that is Gold rated 🙂

[kwelz]

I was actually thinking about one of these two.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817139057

or

http://www.newegg.com/Product/Product.aspx?Item=N82E16817256088

[Chino]

kwelz wrote:
I was actually thinking about one of these two.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817139057

or

http://www.newegg.com/Product/Product.aspx?Item=N82E16817256088

Are there plans to add another 780Ti down the road?