appiah4 wrote on 2020-06-20, 23:13:

I was testing some stuff on my 486 and it started acting strangely. First, it intermittently stopped registering key presses from one keyboard. I then replaced the keyboard and booted it up, and it spat out a Keyboard error at post, no power to the keyboard. I replaced it with yet another, this time the keyboard worked but I still got a Keyboard error at POST I could bypass with F1. I thought the connector may be flaky so I took the motherboard out and inspected it but it's fine. I put the PC back together and this time I got a CMOS error and a Keyboard error and all the CMOS data was gone. The board has a Tadiran 1/2AA Lithium battery on it, non-rechargable (factory installed) and it's easily 25+ years old. I'm certain it's on its way out. I ordered a replacement and I'll solder that in its place, but I was curious as to whether a dying CMOS battery can cause these kinds of keyboard issues..

It could, I think it depends on how the Keyboard controller and what ever chip the BIOS cmos is in are wired up. Have seen some odd setups where the board will not boot at all with dead battery, or boots with all kinds of errors not cmos related with dead battery. Do you know where the cmos actually lives ? Is it in a i/o chip like some UMC, SIS, etc started doing back then ?

Horun wrote on 2020-06-21, 01:13:

appiah4 wrote on 2020-06-20, 23:13:

I was testing some stuff on my 486 and it started acting strangely. First, it intermittently stopped registering key presses from one keyboard. I then replaced the keyboard and booted it up, and it spat out a Keyboard error at post, no power to the keyboard. I replaced it with yet another, this time the keyboard worked but I still got a Keyboard error at POST I could bypass with F1. I thought the connector may be flaky so I took the motherboard out and inspected it but it's fine. I put the PC back together and this time I got a CMOS error and a Keyboard error and all the CMOS data was gone. The board has a Tadiran 1/2AA Lithium battery on it, non-rechargable (factory installed) and it's easily 25+ years old. I'm certain it's on its way out. I ordered a replacement and I'll solder that in its place, but I was curious as to whether a dying CMOS battery can cause these kinds of keyboard issues..

It could, I think it depends on how the Keyboard controller and what ever chip the BIOS cmos is in are wired up. Have seen some odd setups where the board will not boot at all with dead battery, or boots with all kinds of errors not cmos related with dead battery. Do you know where the cmos actually lives ? Is it in a i/o chip like some UMC, SIS, etc started doing back then ?

It is indeed a SiS 471 with the BIOS sticker on the KBC chip:

Are you sure it didn't leak ?

You reminded me of an issue I had recently on my Win98 box, which would randomly lock up completely. I ran through all the usual fault finding, reseating, even replacing components to no effect. Finally my eyes went to the CMOS battery, a button battery in a holder. I noticed the battery was a thinner one than intended, so was not quite as snug in the holder as it should be.

I raised the question online, not really thinking that could be it. And the general consensus was no, that will not be it. But it was due for replacement anyway, so I put a properly sized one in, and the lockups went away.

I could only surmise that the battery was making poor contact, which had some obscure downstream effect on something somewhere!

Deksor wrote on 2020-06-21, 07:56:

Are you sure it didn't leak ?

It is a Lithium battery, extremely unlikely to leak.

I have a sony vaio pcv-120 (200mhz mmx), which has all kinds of video and other issues when the 2032 battery dies out. I replaced it with a dollar store battery and forgot about it, then had all kinds of issues all over again 2 years later when it crapped out. "it can't be the battery, i changed it". I was wrong. Now I buy only name brand batteries.

TLDR: yes it can, change it before you go hunting further!