What happens if I clear CMOS when running the computer?

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Platinum Member
Apr 3, 2020
Might seem to be a stupid question, but what happens if I accidently would clear CMOS when the computer is up and running?

It is possible the real time clock would cease functioning while you had the jump in the clear position, resulting in the software hard crashing. However, it would do no harm to anything, and normal function would resume when you put the jumper in the correct position.

ps: I once installed a 486 90 degrees off angle. Now that let the magic pixies* out!

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Junior Member
Jan 25, 2022
when you push CMOS clear switch, or remove the jumper from one position to another, two actions happens; 1- battery gets disconnected from the CMOS voltage supply rail. 2- the voltage supply rail is shorted to ground to drain the charge. If the power to motherboard is on during this process, I am afraid, the voltage supply rail of CMOS gets shorted to ground, current would surge through all capacitive and inductive elements on that supply rail to ground, the power supply observing a short circuit automatically shots down, and most likely damage to the motherboard, where the damage occurs is anyone's guess. The component connected to the same voltage supply rail of the CMOS are in the front line to withstand the current surge.