Is -5V really necessary? What is it used for on the MB? What if the motherboard is older (ie not ATXV2.2) but the power supply is a v2.2 ATX specification without -5VDC? Can the MB be used with the newer power supply without -5V? I'm no expert at the ATX Power specifications, but V2.1 includes -5V, but v 2.2 does not. And then there the ATX12V Version 2.2 that also doesn't include -5V. Why the differences, I don't know, and what are the implications? I just installed a Zalman ZM460B-APS to my (now aging) Abit NF-7S motherboard and the Abit EQ monitoring software started beeping away with a 'reading' of +3.6V on the -5V rail. Now, I assume this is wrong, on the basis that the Zalman Power supply conforms to the ATX12V version 2.2 spec, which I now know, has 'no connection' on the -5VDC pin. But not knowing what was causing the problem at the time (I suspected my new power supply was a dud), I reverted to my old supply, but it seems as though the motherboard was otherwise operating ok, without a -5V rail. Abit's documentation gives no clear guidance on whether -5V is required - but it does show a negative 5VDC pin on the ATX power connector. So presumably it is used for something, but seems to work without! So, I'm wondering what is the -5V used for? is the lack of a -5VDC rail on the power supply and issue when used on my ABIT NF-7S motherboard. Can I re-install the Zalman power supply with the Abut NF-7S, and disable the Abit EQ alarm for -5V without problems?