A question about the negative 5 volt rail on my power supply.

  I have an older power supply with a -5v rail and an MSI K7N2-6570
motherboard.  With this combination, the BIOS shows voltage on the -5v
rail, but if I put in a different power supply that doesn't even
support a -5v rail, I get 0.00 voltage in the BIOS.  I know what you
are probably thinking, "duh! of course you won't see voltage if you
don't have the -5v rail.".

My question here is, if my newer power supply doesn't support the -5v
rail, and the motherboard is expecting it, will I have any problems?
The system ran fine through POST, and memtest x86, but it wasn't kept
on for much longer after that.  What would the motherboard be
utilizing a-5v rail for?  Will the motherboard malfunction without
this -5v rail?  Any chance of damaging anything by not supply this -5v
rail?

TIA :)

 
If I recall correctly some early memory chips required -5 volts. It has been a
few years since any chips required it and most power supplies now do not have -5
volts.

jaypee68@gmail.com wrote:

  jaypee68@gmail.com wrote:


Some old MBs or ISA cards required -5v. It was removed from the ATX PSU
specification in 2002. Read:

http://www.playtool.com/pages/psurailhistory/rails.html

 On Thu, 11 Oct 2007 07:16:05 -0700, jaypee68@gmail.com
wrote:


As the other replies indicated, you don't need -5V, and it
was probably poor judgement for the bios to have a
monitoring/alarm function for it when it isn't used.

No chance of damage, providing the PSU is decent quality and
appropriate for the system otherwise, basically meaning it
would be new enough to have sufficient current on 12V rail
for CPU VRM supply plus the hard drives and video card (if a
power hungry gamer model).

 
Don't the hard drives use the 5v rail? They have wiring for it.