-12V rail

[angelicvoices]

What exactly does the -12V rail power? I can never find any info on the -12V and -5V rails.

 

[jeremyshaw]

One of the two were for some special, older, ISA slot cards.

The other one.... I don't know!

 

[Elios]

-5v was for some ISA and older PCI stuff latest ATX specs nixed the -5v
-12v not sure on but its still around

 

[Elledan]

-12V is used for COM ports and other legacy I/O. These days this signaling voltage is often generated on-chip, but is still present on the ATX connector for compatibility purposes.

-5 as said was used with some ISA cards (mostly sound cards, IIRC), and there hasn't been any need for it since the late 90s.

 

[[Spectre]]

-5 as said was used with some ISA cards (mostly sound cards, IIRC), and there hasn't been any need for it since the late 90s.

There are a few exceptions to this, with one big one being the SoundBlaster audio setups on some MSI s939 boards.