-12v Line

[Thor]

Does anybody know what the -12v line (from the psu) does on the motherboard, as I can't seem to find anything about it other than the cable is blue!

Thanx

 

[K404]

Adapted from a convo with Persivore:

AFAIK it was used for the RS232/serial voltage levels but there's probably other stuff its used for too

It cant be 100% obsolete or the latest ATX revisions wouldnt have it although... too many mobos still have serial ports, it might just be for legacy stuff

I would have thought they would use a charge pump to generate the negetive voltage now anyway- a charge pump built into the motherboards serial output

it looks like there's a pin for -12v on the PCI connector so its probably for legacy stuff. There's no -5v on there tho which might explain why thats been removed from most PSU's

Is there a fail-safe built in to cause a strop if its not connected? : don't know...the hardware monitor might complain, but I wouldn't think anything else would mind, unless its used somewhere on the board

Hope that makes some sense.

Thanks Tom!

Kenny

 

[Thor]

The plan is to run a 24v fan (max 0.26A and the -12v rail is 0.8A). I don't think it will overload the -12v rail but wanted to try to find out what it runs to see what load it normally handles.

I think I read an article a few years ago about it (-12v line) being used to turn off the computer but not sure of that and done a lot of drinking and sleeping since then so cant remember. (Might just be my imagination)