Purpose of the Type 2032 button cell found in a desktop PC?

[GreensandsParticipant @greensands]

My HP Desktop computer has suddenly failed to start up after some weeks of being left idle, the screen defaulting to the sleep mode and I am left wondering if the cause might be due to the BIOS coin cell type 2032 battery needing replacing. Judging from the LED start-up indicators the main PSU seems in working order but is it possible that it could be due to a faulty coin cell as I have no idea as to what this battery actually does. Can someone please put me right on this.

[GreensandsParticipant @greensands]

[Roger WoollettParticipant @rogerwoollett53105]

It keeps the clock going when the computer is disconnected from the mains.

[Ady1Participant @ady1]

Very important that you renew it or things can get very weird

Then reset your clock in bios to the right time if you can

A lot of software uses date stuff and it gets even weirder on the internet, a lot of sites won't even let you display a page

Edited By Ady1 on 08/02/2023 16:03:46

[lee websterParticipant @leewebster72680]

The button cell, if made in a certain country that is big on spy balloons, contains software that will send your browsing details back to said country and they will target you with suitable ads. Plus what the others said.

[SillyOldDufferModerator @sillyoldduffer]

Posted by lee webster on 08/02/2023 16:32:29:

The button cell, if made in a certain country that is big on spy balloons, contains software that will send your browsing details back to said country and they will target you with suitable ads. Plus what the others said.

As the whole computer was probably made in the PRC, there's no need to go to the trouble of embedding software in a battery, and arranging some way of getting into memory. Much easier and less obvious ways of doing it.

The real purpose of the cell is to maintain a real-time clock whilst the computer is disconnected from it's normal power source. Date-time is important for a myriad of purposes, for example knowing which files to backup, and confirming security certificates are valid. Correct operation of the clock becomes ever more important depending on what the computer is doing. Not too bad on a stand-alone machine that's never connected to anything else, but mission critical on a internet server.

Time is so important that Internet connected computers only rely on the standby clock and battery briefly. When a connected computer boots, it tries to set the main clock from internet time almost as a first step. If this works, the owner may not realise he has a flat battery, because the main clock took over pronto. However, chaos ensues if the battery is flat AND internet time isn't available for some reason. Then all the timestamps essential to time critical functions will be wrong. When the clock is eventually corrected, chunks of the system will be inconsistent, which can cause weird bugs. The effect is a little like radiation: a short exposure to a time error could be harmless, but the risk of fatal damage rises as time passes. Rises much faster on a computer with a complicated workload than one that does a bit of browsing and email..

Normally cells last for several years. Most likely to fail on little used machines kept in cold rooms, or elderly computers. Sometimes annoying to find that cells can be amazing difficult to to replace, hidden away under other components, making it necessary to dismantle most of the machine, and occasionally soldered in…

Dave

[Phil WhitleyParticipant @philwhitley94135]

It maintains a memory bloc where the bios manual settings are stored. For instance, one of the things set by the bios is where the operating system is stored, it may be on a hard drive, a ssd, or whatever, but this destination is set in the bios settings so the computer knows where its operating system is. This (and other settings) are maintained in memory by the bios battery under the "first boot device" setting, and must be maintained in order the computer can go there on boot up, find the operating system and run it. If the bios battery fails the motherboard will return to its default setting and if the default drive is not the drive where the OS is stored, it will return "OS not found" or similar. If you keep noticing the computer time is wrong, or the keyboard goes back to US settings, it is time to replace the battery, but you will then have to reset the bios manually. Not difficult, but you need to know what you are doing!

Phil

[old martParticipant @oldmart]

It maintains the BIOS settings, the real time clock and also any BIOS password that has been put in. Handy if you forget the password, and computer thieves will know all about this weakness. You usually have the option of momentarily shorting out the BIOS reset pins, or removing the cell for a few seconds.

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