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I just inherited a box with an ASUS P5GZ-MX mother board. I have attempted to install two nVidia PCI video cards. I put a 750w power supply in the system to be sure I have enough power. With no extra video cards, the 3.3 v shows normal.

When I put one card in, the 3.3 goes to 3.5-3.6 and flashes red (over voltage) about 30% of the time. When I put the 2nd card in, it goes to 3.73 v and stays red all the time.

Any Ideas why the voltage goes up when I add cards instead of going down? More Importantly, is this dangerous to the system?

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There's no such thing as a "dumb question" :) – squircle Apr 12 '10 at 2:05
Just curious, where are you measuring the voltage? Voltage is highest at the source (power plug) and lowest at the destination (load). – hanleyp Apr 12 '10 at 2:34
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1 Answer

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One thing that would raise the voltage of the 3.3V rail is being tied to a higher-voltage rail. Check the cards in another system to see if they exhibit the same problem.

Overvoltage can be a problem because it applies more electrical stress to components in the system, which can cause failure.

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+1 Definitely sounds like a power-to-power short. Need to make sure cards are seated properly and aren't touching anything conductive. – hanleyp Apr 12 '10 at 2:29
The power supply is a Ultra LSP-750. I removed the two PCI video cards and inserted a TV card in the PCI-E 8 slot and with that card alone the 3.3 went to 3.7+ volts. I suspect that it is just a junk power supply. I know, I know, You get what you pay for. It was a medium priced supply at Comp-USA. Thanks for your suggestions and ideas. – CurtTampa Apr 20 '10 at 19:36
I was reading the voltages in the Bios Screen. It was showing all voltages, fan speed, temp etc... – CurtTampa Apr 20 '10 at 19:38
But a voltage increase is bizarre. Normally the voltage is supposed to decrease when you increase the load on it. – Ignacio Vazquez-Abrams Apr 20 '10 at 21:59
I hear ya Ignacio, I know this makes no sense. That's why I'm here asking the experts. I am an old programmer, not a hardware guy. – CurtTampa Apr 22 '10 at 12:38
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