what does -5 and -12 rails do?

[satanicoo]

Because my PSU has some very strange values on it and it works fine!
Explain to me what they do. Tryed to google but no luck.

[Groth]

-12 and -5 are relics from the days of ISA cards. These days, -5 will be used by the serial ports and nothing else. Your -12 is likely entirely unused.

Your strange reading are a byproduct of how hardware monitoring is done. MBM reads an 8-bit number from a register, runs it through a standard formula, and spits out a voltage reading. Problem is, MBM (or any other program) can't see how the motherboard is wired up; it has to take it on faith that a given register represents a given voltage.

If your board maker has decided that Vdimm is more interesting than -5V, and hooked it up that monitoring line (and register), MBM will give strange results. What you need to do is find out what voltages are monitored, and tell MBM how to interpret them. Best place to start? The MBM homepage - it should have a cross reference board vs. voltage set-ups.