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How do I determine if my computer's CMOS is totally fried? Answered

Yesterday I got a call from my wife that she was bringing the computer back up (there had been a storm and she SAI(D she shut everything down normally and unplugged everything),  and she has this "message" that CMOS had failed and was loading default......press F1 to continue or F2 for set up.

Sadly, neither option actually works.  It  "sounds" like it is processing (looping?) but nothing happens.   Turning it off, waiting and back on again produces the same results and it doesn't get far enough into the boot process to access either the CD or the HD.

Give it to me straight....it's brain dead, right?


It might not be... Go to this link, and then click on the CMOS Checksum Failed link (it will open a popup). It explains in detail what's happening and what you should do at this point.

Check the voltage of the battery as well.

I usually get that F1 F2 message when the CMOS has restored to defaults - in which case it's looking for an nonexistent diskette drive.

Try looking for a clr_cmos jumper on your mainboard. Should be 3 pins, with a jumper over two of them. Switch the position of the jumper, turn on the computer (it shouldn't do anything) turn it off, switch the jumper back, and see if the CMOS resets. You could alternatively remove the clock battery on the MB, it has the same effect.

Is the keyboard fully functional? Test it on another computer. If it's a USB keyboard, try a PS2 keyboard instead.


6 years ago

From reading the threads I think you have hinted at what could be a large part of the problem. Get a new battery before you try and do anything else. At one time having a working battery was critical because the chips lost all the data if they lost power. Now they are flash memory, but the whole bios set up may still rely on some battery power for some things besides the clock. It could need the battery power to write changes to the flash memory. BIOS are very different from one to the other so this may not be a factor, you dpn't know. So start with a cheap 3 dollar battery because it could be the fix you need. If that doesn't work then move on to other things.

And by the way what I would next is start looking for a flash update from the motherboard maker.

And another possibility is a failing power supply. The voltage for the MB may be faulty.

The battery has been low or dead for quite awhile now.

Yes, the CMOS battery on the mother board has been low enough to make me have to reset the date IF the system it turned off for any length of time. That has been happening for nearly a year though. This is the first time I have encountered this message.

Then my guess is the battery is now completely dead, and during the boot the system is trying to go with a default setting. Usually the other causes of this error is a virus or some other motherboard issue, but since you know the CMOS battery has been going, I'd bet its the reason now.

So, do you think a battery replacement will "fix" it (allow it to boot up far enough to get INTO the CMOS settings) ?

If that's the only problem, then yes, replacing the battery should get it working again.

Thank you. I was afraid I was going to have to replace the computer.....

Well the good part is the CMOS battery shouldn't cost you much at all. Then you'll know if that was in fact the only reason (I suspect it is), but there are other things that can be checked, so I would do that first, and then other options can be explored once we're at that point.