OK.... so what is this blog article all about.... Sometimes you will notice that the Power Supply that you have inside your computer has a wire on pin 18 of the main power connector, and the power supply does infact supply a minus 5 voltage supply. No, look, you may be wondering what is that -5 volts for and why is it that some power supplies seem to have a -5 volts supply and others simply do not have that at all.???

On Power Supplies that have no wire in pin 18 you have effectively no - 5 voltage supply.....The -5 volt supply is something that was common on older computers and was for the ISA Bus. You probably remember that this was in effect a slot on the mother board and in fact there was an ISA and an enhanced ISA slot, otherwise knowen as EISA Slot.


As far as I remember EISA slots were usually brown or a creamy colour, and you will find I think that if your computer motherboard does have PCI or PCI Express slots on it, that it will definately not have EISAS or ISA slots and therefore no - 5 volts will be needed.

Essentially, if you are replacing a computer power supply that does have a - 5 volt supply with one that is more modern that does not have a - 5 volt supply you will normally not have a problem..... unless your mother board is very old and has EISA or ISA slots on it.....

Nearly all modern power supplies like Corseair OCZ, and the like, will not supply minus 5 volts to your Computer main board or indeed to any other part of your computer!!!!