Can a completely dead cmos battery prevent a machine from turning on at all?

[bgc99]

Can a dead cmos batter prevent a machine from turning on at all?

BGC

 

[lopri]

Sure

 

[mlc]

I don't think so... but I could be wrong..

My understanding is that the battery is just used to retain settings within the BIOS.. If the battery was going bad, you'd see some tell tale signs before it died completely... and they would include the date/time settings being lost... CHECKSUM errors when you boot up.. and if you overclock.. you'd get warning about settings being lost, etc.. I'm pretty sure it would at least try to post... In fact, I think you can even remove the battery , and the board would power up.. but it would simply read the default settings from the bios chip.... but I'm not 100% sure....

If you are not getting any power at all... that would suggest something along the lines of a power supply issue, or something not seated correctly (video card).. or something shorting out the board (connectors into hard drives, floppies, or the board itself shorting out against the pc case).. or it could be a faulty PC Case Switch.. (you can rule that out by removing the case switch connectors into the board.. and then try shorting out the 2 pins with a screwdriver, to see if it starts up)....

If you've tried to clear the CMOS/Bios.. and left the 3pin jumper in the reset position, that could cause a problem as well.....

Hope this helps....
Mike

 

[Ksyder]

I've seen pc's running with no cmos battery at all... so I'd say that if the machine is not posting, something else might be wrong.

 

[MStele]

The battery just provides enough juice to keep the settings. Your system should be able to boot with a dead battery, but it will keep forgetting your settings. At least that is how its been traditionally. Things can change I guess.

 

[SergeC]

It's happened to me before, so yes.

 

[Ayah]

It just reverts to the bios failsafe settings after you turn it off.

 

[bryanl]

Lack of a working CMOS battery normally makes computers turn on immediately when AC power is applied, but I had a Pentium I motherboard that would not work without a battery, thanks to the manufacturer leaving out 1 diode between the battery and clock chip.

 

[FSH42NA]

I always thought that the CMOS battery is just there to retain the bios settings when AC power is shut off. I wouldn't think it would prevent the pc from booting up at all (but I could be wrong). Worse thing would be you lose your bios settings, time, date,etc.

 

[Lazlo Panaflex]

My In-laws have an older Athlon XP box with a dead battery. Throws the checksum error at POST, & the date in Win XP gets messed up. Other than that, it runs fine.

 

[hanspeter]

When the PSU is powered and plugged in then the battery has no effect, being flat or not. CMOS will be driven by the PSU.