Tom's Hardware > Forum > CPU & Components > Other Components > Is the -12 voltage normal to be out of 5% range?

Is the -12 voltage normal to be out of 5% range?

Forum CPU & Components : Other Components - Is the -12 voltage normal to be out of 5% range?

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mixerman   06-23-2003 at 04:33:16 PM

I was setting up Motherboard Monitor 5 on one of my computers last night and the alarm kept going off for my -12 voltage rail. It kept going out of the 5% tolerance. It got down to: -11.12 Volts at one point last night while the computer was just sitting idling... no load on it. This is almost an 8% change in the voltage. Is this normal on the -12 volt rail? All of my other rails are fine and pretty much stable within the 5% tolerance.

Can somebody please explain what these -12 and -5 volt rails are for? Should I even be concerned with them?

Thanks..

My system:
P3 850mhz (100fsb), 512 Micron PC133, Abit SE6, IBM Deskstar 75gxp (60 gig @ 7200rpm), Hercules 3D Prophet 2 GTS (64 meg), SB Live MP3, Pioneer 16x DVD, Asus 45x CD-Rom

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camieabz   06-23-2003 at 05:40:14 PM
- 0 +

Gotta spec sheet for your PSU?

Some have the tolerances in print.

<b><font color=blue>~ <A HREF="http://forums.btvillarin.com/index.php?act=ST&f=41&t=324&s=58e94ba84a16bedfebbf0f416d5bac48" target="_new">System Specs</A> ~<font color=blue></b> :wink:

Reply to camieabz
mixerman   06-23-2003 at 05:57:09 PM
- 0 +

No it's a P3 850mhz (100mhz fsb) I can't find the spec sheet online..

My system:
P3 850mhz (100fsb), 512 Micron PC133, Abit SE6, IBM Deskstar 75gxp (60 gig @ 7200rpm), Hercules 3D Prophet 2 GTS (64 meg), SB Live MP3, Pioneer 16x DVD, Asus 45x CD-Rom

Reply to mixerman
camieabz   06-23-2003 at 06:55:51 PM
- 0 +

It's just guesswork until you know the specs for your PSU, but a decent PSU will have +/- 5% or 10%.

Generic PSUs will be a less.

<b><font color=blue>~ <A HREF="http://forums.btvillarin.com/index.php?act=ST&f=41&t=324&s=58e94ba84a16bedfebbf0f416d5bac48" target="_new">System Specs</A> ~<font color=blue></b> :wink:

Reply to camieabz
svol   06-23-2003 at 07:16:42 PM
- 0 +

Well the -12V and -5V are really unimportant railes (and to be honest I don't have a clue where they're used for). I've seen bords reporting them at -13V constantly without problems. Most motherboards don't even read those voltages.

So in my opinion you don't have to worry.

My CPU fan spins so fast that it creates a wormhole :eek:

Reply to svol
mixerman   06-23-2003 at 07:20:58 PM
- 0 +

Okay thanks.. so what are all the voltages that I am MAINLY concerned with being in the 5% tolerance and that I should monitor and set alarms for in MBM 5 ??

My system:
P3 850mhz (100fsb), 512 Micron PC133, Abit SE6, IBM Deskstar 75gxp (60 gig @ 7200rpm), Hercules 3D Prophet 2 GTS (64 meg), SB Live MP3, Pioneer 16x DVD, Asus 45x CD-Rom

Reply to mixerman
svol   06-23-2003 at 07:42:47 PM
- 0 +

The 3.3V, 5V and 12V from your PSU and the VCore and if possible Vdimm from your motherboard.

My CPU fan spins so fast that it creates a wormhole :eek:

Reply to svol
mixerman   06-23-2003 at 08:31:04 PM
- 0 +

What's the Vdimm? My motherboard has the CPU core voltage and some other voltage that is: +1.5 volts.... I don't know what this one is called..

My system:
P3 850mhz (100fsb), 512 Micron PC133, Abit SE6, IBM Deskstar 75gxp (60 gig @ 7200rpm), Hercules 3D Prophet 2 GTS (64 meg), SB Live MP3, Pioneer 16x DVD, Asus 45x CD-Rom

Reply to mixerman
camieabz   06-24-2003 at 03:10:05 AM
- 0 +

The 12V and 5V are unimportant?????

You're kidding!

Molex connectors, HDDs, CPU, mobo, gfx you name it.

Memory runs on the 3.3V rail alone, but almost everything else runs on the 5V and/or 12V.

<b><font color=blue>~ <A HREF="http://forums.btvillarin.com/index.php?act=ST&f=41&t=324&s=58e94ba84a16bedfebbf0f416d5bac48" target="_new">System Specs</A> ~<font color=blue></b> :wink:

Reply to camieabz
Crashman   06-24-2003 at 06:32:37 AM
- 0 +

d00d, he said NEGATIVE 5v and NEGATIVE 12v were unimportant, and he's probably right. I don't know of any part of a modern PC that uses them.

<font color=blue>Watts mean squat if you don't have quality!</font color=blue>

Reply to Crashman
camieabz   06-24-2003 at 01:30:53 PM
- 0 +

aahhh. Cool. My mistake.

<b><font color=blue>~ <A HREF="http://forums.btvillarin.com/index.php?act=ST&f=41&t=324&s=58e94ba84a16bedfebbf0f416d5bac48" target="_new">System Specs</A> ~<font color=blue></b> :wink:

Reply to camieabz
svol   06-24-2003 at 06:31:26 PM
- 0 +

LOL... read first.

My CPU fan spins so fast that it creates a wormhole :eek:

Reply to svol
svol   06-24-2003 at 06:32:57 PM
- 0 +

The Vdimm is the memory voltage.

I think that 1.5V is your AGP slot voltage.

My CPU fan spins so fast that it creates a wormhole :eek:

Reply to svol
lhgpoobaa   06-27-2003 at 02:34:51 AM
- 0 +

Yes... In my experience the negative rails can vary significantly, but rarely is an issue. Especially as the load on them combined is less than 1A usually.

The 5v and 12v are very important, a bit less so the 3.3v... but all should be within +/- 5%.

If one has a weak/poor PSU, the P4's show this on the 12v line, and AMD systems it shows up on the 5v line.


<b>Melb_angel: PooBaa's <A HREF="http://www.secretarythemovie.com" target="_new">Secretary!</A></b>

Reply to lhgpoobaa
svol   06-27-2003 at 03:54:52 PM
- 0 +

Actually most AMD board for Athlons use the 12V railas power source, except for Epox who is rumoured (which is probably true according to my experience) to use the 5V rail.

My CPU fan spins so fast that it creates a wormhole :eek:

Reply to svol
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