Sign in with
Sign up | Sign in
Your question

Best way to clear CMOS?

Tags:
  • Homebuilt
  • Computer
  • Power
  • CMOS
  • Jumper
  • Systems
Last response: in Systems
Share
October 18, 2008 12:52:39 AM

So I need to try to clear my CMOS because I have a computer that won't turn on. I tried doing this a couple of times but want to make sure I am doing it right as my computer still will not power on.

First I unplugged power cord. On my mobo there is a jumper, so I took it off pins 2 and 3 and moved it to 1 and 2. After 5 minutes or so I put the jumper back on 2 and 3. Plugged the power cord back in and tried to power up, nothing happened, no post, no beep.

(1) Should I plug the power cord in while the jumper is on clear or leave power cord unplugged?
(2) Is 5 minutes enough time to clear CMOS or should I wait longer?

Lastly, I tried taking out the mobo battery as well. I unplugged power, took out battery for about 20 minutes, put it back in, plugged in power and tried to power up from there, also with no luck.

(3) So how long should I leave out the battery? I have heard anywhere from 1 minute to 8 hours, so which is it?

Thanks for the help.

More about : clear cmos

October 18, 2008 1:02:31 AM

you've cleared it already so it must be something else.

New build? Get anything at all, beeps? fans spin? Lights? Anything on monitor at all?

oops, re-read your post and I see yo got nothing.

Check and db check all power hookups - main, 4/8 pin cpu aux., video power
October 18, 2008 1:52:07 AM

If everything is plugged in right --20/24pin and 4/8 pin-- which ever of those are more appropriate for your setup then I would look to the PSU as being dead because you've definitely cleared the cmos.

Got another PSU you could try?

also, what are your specs? and does your MB have any lights on it?
Related resources
October 18, 2008 2:33:51 AM

-- Alright, so I cleared the CMOS correctly, that's good to know but still, no luck.
-- I have put a brand new PSU in the computer as well, still no power
-- Took out all but one of the memory sticks
-- Took out graphics card
-- Disconnected HD's

Yes, there is a green light on the mobo. Does that mean it is still alive or just that it is getting power?? I am ready to replace the motherboard, can't think of anything else really.

The system is an old Gateway, 3 years old with some generic Intel board
Pentium D
2gb PNY ddr2 4200
BFG 550watt PSU
Radion x800
October 18, 2008 4:14:13 AM

Well, if it's an old PC and you are sure all the power connections are good and you have tried a new PSU then a bad mobo is probably number 1 suspect.

However, one thing we always try before assuming a board is dead is rebuilding the PC outside of the case, with the mobo sitting on a non-conductive surface and all unneeded devices removed from the system..

This achieves the re-seating of all power connections, and of all the cards and the ram sticks in their slots, (a frequent issue with old PCs is poor connections in the slots) and it also removes a shorting case, or bad.shorting power/reset switch from the situation. Once you have rebuilt it barebones outside of the case you simply short the power pins with a screwdriver to start it up. It is possible you just have a bad switch.

Of course if possible you try to switch in known working ram and video cards too before you assume it is mobo. In MOST cases if it is ram or video you will at least get an abortive power up and POST attempt and then some error beeps, but not always.

CPUs, unless severely over-volted or run without cooling. almost never go bad so it is usually a safe bet to rule that out.
October 18, 2008 5:15:48 PM

Thanks, that's very helpful. As of today, I am setting out to buy a new motherboard. A friend just gave me an old case, so I am going to re-build this computer in the new case, with a new motherboard. I just need to find a mobo that supports a Pentium D. Then I will try to run a windows repair. I well get back to you with the results. I just hope everything works out!
!