voltage variation

**lonewolfroger** · 10-20-2003, 04:05 PM

I have a Enermax 431w PSU and on one MB the +12v rail will stay below the 12v`s to 11. something volts and on the MB I have now it stays above the 12v`s. It has never been over 5% out of specs either way I was just wondering if there was a differance between it being above or below the actual voltage.

**enigma325** · 10-20-2003, 04:33 PM

It's probably not the PSU but the motherboards giving the wrong readings, I might be wrong but from what I've heard most motherboards aren't as accurate as we'd like them to be. Mine reads that my +12 is around 11.67 with any power supply I put in.

I do think that slightly higher is more desireable than low for ocing at least.

**xDUCK** · 10-20-2003, 04:42 PM

Higher is good, lower is bad. I modded my PSU and my rails are now (mobo reading - multimeter reading is about 0.2v higher) 3.4v, 5.1v, 12.2v. I don't have time to explain why high rails are important (just on my way out), I'll post later (or PM me).

Edit: Those rails are under 100% full load (Prime95, Folding@Home, and web browsing etc).

**proxops-pete** · 10-20-2003, 04:44 PM

In short, always use an actual voltmeter to read accurately. Mobo voltage readings/measurements are convenient to have, but were never meant to be very accurate.

**xDUCK** · 10-20-2003, 06:01 PM

Originally posted by proxops-pete
In short, always use an actual voltmeter to read accurately. Mobo voltage readings/measurements are convenient to have, but were never meant to be very accurate.

Actually, while mobo readings aren't DEAD on, they are more accurate in terms of actual voltage than a multimeter. Say the PSU outputs 3.4v (on the 3.3v line) - a multimeter will read 3.4v, alright, but by the time the current works it's way down to to the places where it is used, some of it is lost (in the form of heat, which can be observed pretty easily

). So even though your PSU is outputting 3.4v, it is reduced by the lack of 100% efficiency in the motherboard's electronics.

**lonewolfroger** · 10-20-2003, 06:06 PM

xDuck, running with the specs in my sig. with 4 80mm fans, a 120mm fan, my 92mm tornado going full blast. My voltages are a little over +12.4v`s for the +12v rail and around 4.8v`s on my +5v rail. the actual voltages are on page 3 on my website, in which there is a link to it in my sig.

**xDUCK** · 10-20-2003, 06:14 PM

Originally posted by lonewolfroger
xDuck, running with the specs in my sig. with 4 80mm fans, a 120mm fan, my 92mm tornado going full blast. My voltages are a little over +12.4v`s for the +12v rail and around 4.8v`s on my +5v rail. the actual voltages are on page 3 on my website, in which there is a link to it in my sig.

So what do you need me to do?

Raise your 5v and your 3.3v then (PSU mod). 12.4v is just fine for a 12v rail.

**lonewolfroger** · 10-20-2003, 06:16 PM

Originally posted by xDUCK

So what do you need me to do? Raise your 5v and your 3.3v then (PSU mod). 12.4v is just fine for a 12v rail.

Nothing,

just wanting your opinion on the +12v rail, thanks.

**Lord Vetinari** · 10-21-2003, 02:46 AM

It is pretty normal for the 12V line to be high when the 5V line is low. The 5 and 12 V lines are linked inside the PSU- if the demand on the 5V goes up (ie high current drain) then the PSU outputs more power on both lines.

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