Changing CMOS Battery In Old Desktop

Malneb said:

There is five requirements to boot a computer plus one optional factor.
- PSU
- CPU
- Ram
- Boot partition(so this means that load order is set correctly and the hard drive with the correct partitions on it)
- RTC is set accordingly.

Optional:
Display output.

No battery will lock you out until you set those settings but its not stopping you. you defualt F2 and then set any other requirements each time you turn on the pc.

You don't need a cmoss battery to fill any of those requirements the computer can do without a battery even, if its not booting without the battery in place then there is something underhanded happening or it was coincident.

I have not seen a case where the computer will not boot without a battery. It could be something that is possible i guess but i have never seen it not that i overly check for this sort of feature either.

Why then did my previous PC fail to boot when the battery voltage fell below 3V? Maybe true for some boards but not all.

I am not sure man but a 2 dollar coin battery is not going to be the Jenga piece that destroys the computer. Like you can boot the computer without one.

Malneb said:

I am not sure man but a 2 dollar coin battery is not going to be the Jenga piece that destroys the computer. Like you can boot the computer without one.

No, you can't always boot without one - see above.

if it was critical then this would not be possible.



if the battery was a hard requirement then the instant you pull that battery from a running computer then the computer would instantly turn off.

The RTC is keeping all other clocks in time because its the main time source for hardware and is tied to CMOS so the inverse logic as stated above is still valid meaning you don't need a coin battery to boot the computer.

I could be wrong it could go both ways i just have never seen it, it could be something that would fall into an OEM PC as a crumby over provisioned feature. I guess if they design the circuit in a way where it knows due to continuity or something then it would be possible.

That would also explain why you mention under 3V as that would be a continuity issue.

I don't design motherboards i just use them.

The battery itself isn't critical but the right BIOS configuration is.

If you have a specific BIOS configuration, that isn't default, if you don't have a battery or it has no charge, when you start the computer it will load BIOS default and it won't boot.

My desktop won't boot with the BIOS defaults. My drive is EFI-GPT and the BIOS default is to boot a Legacy-MBR.
On my very old laptop, it only has a Legacy BIOS so it will boot with the defaults.

Sure but you can still boot the pc. As mentioned you set the settings manually every time and then boot the computer.

woodbine said:

Thanks again for your help - managed to access BIOS settings. Now I have a long list of options, which ones do I need to make a note of? Or all of them? This is my BIOS list -

Product Info-----------------------------------------------PC Health Status
Standard CMOS features----------------------------------Frequency/voltage Control
Advanced BIOS features-----------------------------------BIOS Security Features
Advanced chipset features--------------------------------Load Default Settings
Intergrated peripherals
Power management setup

Also, does anyone know how you go backwards in BIOS settings?

On OEM computers like Acer there are not too many BIOS options.
With a cel phone, take a photo of all pages.

Although it isn't recommended, you can change the battery with the computer off and power cord connected.

@woodbine


That's an even better idea... just take smart phone pics of everything.
I have a smart phone, but I've only had it for about 6-7 months, so I still don't "think" in smart phone, sometimes.