GTX 670 SLI Overclock limited by psu?? help

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theonlyfool

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Feb 13, 2013
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I've been gaming for a while now, and Ive always OC'ed my graphics cards. I have 2 670's running at the moment, and while I was working on the OC for both I noticed something.

While under 100% load, Both of the cards seem unable to reach the OC values I set, BUT if I lower the clock on one card, the other card's clock will increase to the value I set.

Could it be that my power supply, which has 45A on the 12v rail, is insufficient to support both cards fully overclocked? I noticed that the gpu vcore also effects the clock if that matters.

Ultra LSP 750W

Any help would be appreciated

Specs:
MSI Z78-GD65 Gaming
4770k @ 4.5ghz
2x 670 (one EVGA one ASUS) @ 1136mhz
3 hdd's, 2 ssd's
Ultra LSP 750W
 
Solution
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I would not assume an Ultra LSP can output anywhere near what it's rated at. Also any 750w power supply that is a true 750w power supply will provide somewhere around 62 amps on the 12v rail. What you have there if it was rated correctly is a 550w power supply. Amps ( 45 ) x volts ( 12 ) = watts ( 540w ). And once again most units of that quality can't provide rated power under load. So you have a low quality unit ( made by Andyson ) with a liar label.

GTX 670s in Sli require a true 750w power supply.

http://www.realhardtechx.com/index_archivos/Page362.htm

Low quality units also have very high ripple and loose regulation that can damage capacitors on your motherboard and graphics cards over time. They supply "dirty" power. I would be...
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Deleted member 217926

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Ultra power supplies are well marketed junk so it might very well be incapable of powering your system.
 
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theonlyfool

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I have been pretty happy with this PSU despite the fact that its not a major name, but getting down to the technical part of the question, I'm specifically curious is the 45A rail is insufficient. Has anyone had experience with this?

I'm thinking about upgrading to a 1000w or something if this is the case. Or at least to something with a much higher 12v rail amperage.
 
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Deleted member 217926

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I would not assume an Ultra LSP can output anywhere near what it's rated at. Also any 750w power supply that is a true 750w power supply will provide somewhere around 62 amps on the 12v rail. What you have there if it was rated correctly is a 550w power supply. Amps ( 45 ) x volts ( 12 ) = watts ( 540w ). And once again most units of that quality can't provide rated power under load. So you have a low quality unit ( made by Andyson ) with a liar label.

GTX 670s in Sli require a true 750w power supply.

http://www.realhardtechx.com/index_archivos/Page362.htm

Low quality units also have very high ripple and loose regulation that can damage capacitors on your motherboard and graphics cards over time. They supply "dirty" power. I would be very surprised if that unit met ATX specifications. I'm honestly surprised your system boots much less is able to be overclocked.

My advice stands. Replace that thing ASAP.
 
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theonlyfool

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Exactly the information I was looking for, thanks man!
 
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