Are all voltages present at the ISA slot?

yes, i think. going now through the pins with multimeter ...

3e8 is conventionally for COM3:... can you change it to 3f8? It's possible mouse drivers have it hardcoded and aren't looking at the BDA as you pointed out in debug.

edited the original post.
both com1 and com3 are enabled.
tried all possible combinations of controller jumpers and driver parameters to attach to any possible addres/irq.

at the same time everything else works just fine.

Have you tried to use CTmouse, I found on older machine in dos its one of the better mouse driver for serial mouses out there

pshipkov wrote on 2023-06-15, 20:08:

A bit perplexed by this issue. (config and autoexec empty) Not sure how to proceed from here. Any hints ? […]
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A bit perplexed by this issue.
(config and autoexec empty)
Not sure how to proceed from here.
Any hints ?

Hmm sounds like either you did not "install" the mouse driver or you just tried the .com/.exe but did not add it to your autexec.bat manuallly. Just launching the .com/exe will not auto add it.

TxSnipper wrote on 2023-06-16, 01:28:

Have you tried to use CTmouse, I found on older machine in dos its one of the better mouse driver for serial mouses out there

True but Not if you are using a Microsoft mouse and DOS + Win3.x. It can cause problems... If the mouse is not found using MSmouse driver 8.2 or 9.0 then there is a hardware issue..
CTmouse is known to cause some issues with certain motherboards and a DOS+ WIN config.

Should clarify - i use CTMOUSE (whatever was the latest version) and MS MOUSE version 9.01.
They can be initialized from command prompt.

Really puzzling what kind of hardware issue that can be.
Will finish some lookups with the multimeter and oscilloscope later today.
But feels unlikely something surprising will come up.

If you have a spare female DB9 cable/connector you can easily create a loopback adapter like this one and run CheckIt to test the serial port. It's been of great help to me in the past to diagnose broken serial ports.

Looking at this diagram and not sure what i need to “construct” actually.
Probably missing the obvious. Can you clarify please ?

It's a loopback adapter. You connect the pins of the back of the female DB9 as indicated in the table (i.e. pins 1, 4, 6, 9 connected together, then 2 & 3 and 7 & 8 ). And then you plug the DB9 to the serial connector in your computer before running the CheckIt test.

which serial port is the mouse attached to ?

@TheMobRules

Ah, i see. Makes sense.
I don't have such connector available and don't want to ruin a mouse for that.
Going to order one. They are cheap.

@weedeewee
COM1

pshipkov wrote on 2023-06-15, 20:08:

DEBUG.EXE -d 40:0 l8 returns 03 E8 00 00 00 00 00 00 (juuust in case) […]
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DEBUG.EXE
-d 40:0 l8
returns 03 E8 00 00 00 00 00 00
(juuust in case)

I'm a bit perplexed by this.
since according to an internet snippet

1   
2          1st serial port found
3            |   2nd serial port found
4            |     |   3rd serial port found
5            |     |     |   4th serial port found
6            |     |     |     |
7            v     v     v     v
80040:0000 F8 03 F8 02 E8 02 00 00-78 03 BC 03 BC 03 C3 03
9                                    ^     ^
10                                    |     |
11                                    |    2nd parallel port found
12                                    |    
13                                    |
14                                  1st parallel port found 

technically this would imply DOS only sees one serial port COM1, but it's located at the address normally used for COM3.

I tried with F8 03 and any other combinations one can think of.
When i posted here i was at E8 03 combo. I can see how this can be confusing now.
JT1 picked on this as well, but in reality the controller can be configured to use any address really.
https://stason.org/TULARC/pc/hard-disk-floppy … s-PTI-2-26.html
CTMOUSE for example has flags that allow to pick any address/irg as well.

Right now, while typing this, i have LPT and COM2 disabled with jumpers.
COM1 is at F803 and IRQ4, again with jumpers.

If you have a terminal/modem program on the computer and stick a wire between pin 2 & 3 of the com port, anything you type in the terminal (with flow control off), should be echoed back to the terminal.

Leave the port at that first address. you say the card works in another system, so it should be set up correctly.
Only play with the IRQ for a test, standard should be IRQ 4, only one jumper on the first two pins of JP8, second & third should be free.

if it, mouse and or terminal test, doesn't work. Take a multimeter and measure the voltage on ISA pin B24.

pshipkov wrote on 2023-06-16, 03:09:

Really puzzling what kind of hardware issue that can be.

PSU would be my guess. That is, if the port controller card does work in another system. Serial mouse is powered by voltages output by DTR and RTS lines (IIRC) so if these are not in spec, or the card has damaged/weak drivers, there won't be enough power for the mouse. A slightly lower voltage on the PSU rails might be just the difference between working and non-working mouse with the same HW across two different PCs.

I mentioned in my first post that the controller and mouse are fully working.
The issue is with the mobo.

Checked the isa pins - voltages and frequencies check-out.

Will run the suggested loopback tests soon.
The one with terminal +2 connected pins will be first.
The second approach with female connector will wait for the connector to arrive.

I have a Terminal app in DosNavigator. I dont remember ever using it in the distant past. It was not obvious what i have to do really.
Cannot even remember what DOS terminals i used back in the day. Probably some telnet and ssh ports for dos.
Any suggestion what should i try ?

Ok so it works in two other systems, what are they ? Have you tried the IBM/Other jumper (JP5) ?
We need more info or could be guessing all day long so ... what exact 386 mother board ? Is your PSU a true AT or some ATX with adapter ?
Also probably not relevent but why not default Com 1 - 3f8 Com 2- 2F8 (or why Com 3 3e8) ? if not then why not use total default * settings in that Stasons link ?
just thinking about how we really do not know much about the motherboards and why you choose Com 3 instead of disabled for second port....
I know probably not relevent but inquiring minds want to know.