[SOLVED] Why are my CPU power pins at -12V?

Dec 19, 2021
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I found a bunch of diagrams saying that some pins on a 8-pin connector should be at a positive 12V. I tested my 24-pin one and all those came back as the diagrams I googled said they would, but my CPU power ones didn't. I'm testing my power supply because I can't get my computer to boot, is this the reason why or did I just find the wrong diagrams?
 

Krotow

Estimable
Look like mismatched positive and negative multimeter leads :)

Fun fact: In first IBM PC negative voltage was applied to DRAM chip base for substrate bias to make them work right. -5V to be correct. It came in PC realm from 8080 CPU where -5V was required to be applied to chip base as well by same reason. It however wasn't required in PCs already starting from 80186 CPU. -5V was still present in ISA bus and sometimes was used in some extension cards. Though because -12V is also present in AT and ATX PSUs, -5V was obsolete already at nineties. Legacy is strong stuff though - we still have PSUs with -5V around.
 

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