Malke said:
The length of time you need to wait after removing the battery varies.
It can be as short a time as a minute or as long as a day. We've seen
many different time periods be effective. Naturally, if the motherboard
supports clearing CMOS with jumper settings, that is the quickest and
best way to do it.
Malke
--
Elephant Boy Computers
www.elephantboycomputers.com
"Don't Panic!"
MS-MVP Windows - Shell/User
More opinions: (guess I've been lucky)
http://www.techspot.com/vb/all/windows/t-16329-PC-wont-go-to-BIOS-after-removing-CMOS-battery.html
Soul Harvester
10-24-2004, 06:26 AM
CMOS only retains BIOS settings for a few seconds after the battery is
removed. 24 hours is just insane overkill.
Also, on most semi-modern machines, the password isn't stored in volatile
memory and as such will never be "reset" using that method - There will be a
jumper on the motherboard to specifically erase the password. You should
search for that motherboard on the internet and fine the manual for it.
http://www.dewassoc.com/support/bios/bios_password.htm
If the "Clear CMOS" jumpers are not present or not available:
The procedures for clearing a Bios/CMOS without jumpers is essentially the
same as those given above when they are present, it just takes a little more
effort.
*
Shut down the computer and disconnect the power plug.
*
Locate, if possible, the instruction booklet for your motherboard. If
you cannot locate the booklet, then user the motherboard references on this
site to locate the manufacturer and see if a manual is available there. You
may also want to closely examine the motherboard itself.
*
Now identify where the battery is located on the motherboard. It will
be approximately 1/2 inch in diameter.
*
Normally these batteries are held into place with one or more small
clips over the face of the battery. Carefully lift the battery out of its
socket and set it aside. Note: Some batteries are actually soldered to the
motherboard, so take that into consideration and be careful.
*
Leave the battery our of the computer for about 20 to 30 minutes and
then return it to its socket.
*
Now plug the power cord back in and restart the computer.
*
Removing the CMOS Battery
http://www.techenclave.com/forums/how-to-bypass-bios-passwords-5230.html
(this one states 24 hrs).
The CMOS settings on most systems are buffered by a small battery that is
attached to the motherboard. (It looks like a small watch battery). If you
unplug the PC and remove the battery for 10-15 minutes, the CMOS may reset
itself and the password should be blank. (Along with any other machine
specific settings, so be sure you are familiar with manually reconfiguring
the BIOS settings before you do this.) Some manufacturers backup the power
to the CMOS chipset by using a capacitor, so if your first attempt fails,
leave the battery out (with the system unplugged) for at least 24 hours.
Some batteries are actually soldered onto the motherboard making this task
more difficult. Unsoldering the battery incorrectly may damage your
motherboard and other components, so please don't attempt this if you are
inexperienced. Another option may be to remove the CMOS chip from the
motherboard for a period of time.
Note: Removing the battery to reset the CMOS will not work for all PC's, and
almost all of the newer laptops store their BIOS passwords in a manner which
does not require continuous power, so removing the CMOS battery may not work
at all. IBM Thinkpad laptops lock the hard drive as well as the BIOS when
the supervisor password is set. If you reset the BIOS password, but cannot
reset the hard drive password, you may not be able to access the drive and
it will remain locked, even if you place it in a new laptop. IBM Thinkpads
have special jumper switches on the motherboard, and these should be used to
reset the system.
Removing the battery
http://www.elfqrin.com/docs/biospw.html
If you can't find the jumper to flash the BIOS or if such jumper doesn't
exist, you can remove the battery that keeps the BIOS memory alive. It's a
button-size battery somewhere on the motherboard (on elder computers the
battery could be a small, typically blue, cylinder soldered to the
motherboard, but usually has a jumper on its side to disconnect it,
otherwise you'll have to unsolder it and then solder it back). Take it away
for 15-30 minutes or more, then put it back and the data contained into the
BIOS memory should be volatilized. I'd suggest you to remove it for about
one hour to be sure, because if you put it back when the data aren't erased
yet you'll have to wait more time, as you've never removed it. If at first
it doesn't work, try to remove the battery overnight.
Important note: in laptop and notebooks you don't have to remove the
computer's power batteries (which would be useless), but you should open
your computer and remove the CMOS battery from the motherboard.
