I have a machine that I've owned since new. I recently rebuilt it and got it all up and running about 2 years ago. It's kind of just sat since then. It's a GMB 486 UNP motherboard. I had removed the battery those few years ago and used the external battery header with a 3.6v lithium battery pack. IIRC before I fixed the battery it did boot but wouldn't save the bios settings and would complain about low/no battery.

Now when I turn it on, all I get is 10 bios beeps which looks to be "CMOS Shutdown Register Read/Write Error". I don't really know what that means other than a hardware error. I've stripped it down to nothing but the CPU and dip cache and memory and it's still doing the same thing. I tried removing the lithium battery (I'll admit I haven't tested it yet), and resocketing the bios (no corrosion. the only corrosion is around the original battery solder points, it seems fine otherwise.) I've also tried setting JP33 to discharge CMOS for over a day and same thing. (If I turn it on with the jumper set to drain it doesn't beep but it also doesn't do anything, I'm pretty sure you're not supposed to do that.)

I'm kind of at a loss as there's nothing visibly damaged with the board and it worked fine til it sat for a few years. And it's not like it hadn't been sitting for many years before that.

Here's the manual for reference:
http://www.elhvb.com/mobokive/Archive/Gemligh … p/486unp301.pdf