Clarification required on how to clear a mobo's cmos settings \ VOGONS

Clarification required on how to clear a mobo's cmos settings

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First post, by retro games 100

Posted on 2011-12-31, 18:57

retro games 100 Offline

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After testing a PC, I flick the mains power supply switch on the wall to off. Is it then necessary to remove the mains power supply plug from the socket on the wall, before moving the mobo's cmos settings jumper to the "clear cmos" position? Or is it OK to leave the mains power supply plug inserted in to the wall socket?

I've read something about "power cycles" and PSUs. I vaguely recall that if you remove the mains power supply plug from the wall socket, it does something to the PSU's "state", but I can't remember exactly what.

Also, what is the length of time that the mobo's cmos settings jumper needs to be kept in the "clear cmos" position? Does having the plug removed from the wall socket make any difference to this required time? Thanks a lot for any information.

Reply 1 of 6, by DosFreak

Posted on 2011-12-31, 19:05

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I don't have any definite answers for you but what I do.....

Any time I open the case I unplug the PSU.
Any time I remove the CMOS battery I wait 30 seconds before reinserting it.

I think I've only ever used jumpers to wipe the CMOS 1 or 2 times. It's much more of a PITA for me to play with jumpers (or find something to short the pins) than it is to take out a battery.

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Reply 2 of 6, by F2bnp

Posted on 2011-12-31, 19:43

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Yeah, just take the battery out after unplugging the system and wait for a minute or so just to be safe.

Reply 3 of 6, by Malik

Posted on 2012-01-01, 02:21

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Usually, to clear the CMOS, I just short the jumpers - whether or not the mains is plugged in.

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Reply 4 of 6, by retro games 100

Posted on 2012-01-09, 13:49

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Thanks a lot everyone. I do like the sound of removing the battery from the mobo, because that way you know for certain! 😀

Reply 5 of 6, by Tetrium

Posted on 2012-01-09, 16:59

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F2bnp wrote:
Yeah, just take the battery out after unplugging the system and wait for a minute or so just to be safe.

Ftr, this is what I do also. Except that I wait like a couple minutes, just to be sure 😉

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Reply 6 of 6, by maddmaxstar

Posted on 2012-01-09, 20:31

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I usually don't worry about leaving the machine plugged in when clearing the CMOS. Setting the Clear CMOS jumper usually works regardless of power cord state, although I usually flip the PSU's external power switch to off before sticking my hands in a system. If the CMOS doesn't clear on the first attempt, unplugging the power supply and leaving it for 30s may be helpful for troubleshooting.

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