It seems there is another problem with my motherboard. I though just powering the CMOS memory is enough to run it, but now it started giving errors again.
Currently it gives 3 beeps on an AMI bios. It means that there has been a base memory read/write test error in the first 64 KB block of memory.

Is this the conventional memory or the first 30 pins sdram?
There is a chip is61c64ah-15n. What is this chip? It sits aside between the sdram slots and the external cache memory.

this memory error is before cache has been initilized, try four different simms

Yes it was the simms. I just did not want to accept it because I just bought them and 2 out of 4 do not work.
According to the manual the motherboard requires always 4 simms? I mean isn't that too much of a requirement?
https://theretroweb.com/motherboard/manual/31443.pdf
Now I am searching for another 2 simms x 1 MB as the rest are for my base 386.

tonata wrote on 2023-06-11, 16:43:

According to the manual the motherboard requires always 4 simms? I mean isn't that too much of a requirement?

These are the older, "short" 30-pin SIMMs, not the newer 72-pin ones. Each stick provides only 8 bits of data, so for 32-bit CPU like 386DX or anything better you need 4 sticks. Or a multiple of 4 (8 for the usual 2 banks most mobos have).
You can get away with just 2 sticks for 286 (if the mobo accepts SIMMs) or 386SX. Newer 72-pin SIMMs provide 32 bits per stick.

Well actually it's 9 or 36 due to parity (1 bit per each byte) but 72-pins SIMMs usually don't have parity chips. Most mobos are fine with that but if you ever get a mobo with both old and new SIMM slots, beware, it might require full 36-bits on the new SIMMs as well. Might be an option in BIOS to disable that, might not be.

It seems that the CMOS memory is cleared after I save it from the BIOS.
I am using a Li-ion 3.6B battery that I find a bit low for a new one. It is 3.65V when measured directly and 3.30V after the protection diode.
Before it was better I think.
I have installed the 4069 although I do not know for sure if it works.