Could you verify with a multimeter that all the voltages are present, ie +12v, +5v, -5v, -12v ? Verify the voltages on the PSU connector and on the ISA slot.
and if possible post some hi-res photos of only the mainboard since the one on the retroweb is seriously lacking in detail.

Dear Friend, thank you very much for your message. I have found the high-res pictures of the board:
https://www.ebay.com/itm/MITAC-INTERNATIONAL- … 30544621?_ul=IL

I will also check the psu but it is an ATX one Redrock 300 Watt without -5V but I think RS232 will not require -5V but I will upload.

any other ideas?

Timucin wrote on 2023-10-29, 14:02:

The cable is properly connected to the comports on the motherboard, not upside down.
I also bought old cables, but the system does not recognize the mouse

Verify the pinout of the cables and report them back. the arrow on the IDC plug indicates pin 1, and next to it are all the odd numbered ones. The other line contains all the even numbered pins.
On the 9 pin serial connector the numbers might be indicated in the plastic.

I will check and come back to you, thank you very much sir

It is either
12345
6789

Or
1 3 5 7 9
2 4 6 8

So when I look at the cable, I cannot really understand the numbering.
Here are the pictures. Anyone who could identify the numbering for comport?

Mice are working, I controlled them on a XP machine.

You'll need to work out a couple of things. Firstly on your cable which pin on the rectangular connector (IDC connector) goes to which pin on the Dsub connector. Easiest way to do that is probably to take the back off the dsub end of the cable so you can see which strand of the cable goes to which pin on the connector. There are a couple of sort of standards which Evasive gave above.

Secondly you need to find which pin on the motherboard COM port is connected to Ground. Easiest way to do that is to get a multimeter and (with the board unplugged) measure the resistance from each pin to a point you know is Gound (e.g. motherboard mounting screw, or a Ground pin on the power connector). One of the pins should measure around 0 ohms, and that's the Ground pin.

From knowing those two things then you'll know if pin 5 on the dsub (if you look closely you might see each pin is numbered on the connector) will be connected to the Ground pin on the COM port. If it is then it should probably work and the problem might be somewhere else. If pin 5 isn't Ground then you'll need to resolder or modify the cable.

Thank you very much for your helps. But I am not handy really that much. I am interested in social sciences rather but still encompassed within the wind of computers 😀 So I found some RS 232 cables, do you think one of these work? Because the strange thing is even ISA comport didn't work... Finally can it be because of the psu if it doesn't support -5V??? Maybe for ISA card I believe.

https://tr.aliexpress.com/item/10050049055113 … 212234285508%21

https://tr.aliexpress.com/item/10050052977451 … 212234285508%21

Looking at the images, it appears to have a PS/2 mouse header like the one on the right side of this image. I would confirm the +5 and ground with a meter before plugging anything in (just to be sure), but acquiring and (if necessary) rewiring a PS/2 mouse backplate would likely be easier than finding the correct serial port cable, and you'd have a better mouse in the bargain.

I found this but seems already out of stock...
https://www.ebay.ca/itm/391942848851

It's at times like this that I realize that setting up old computers like this really has become a forgotten art as far as most of the world is concerned. Here is a vendor that has what you need, but I have no idea if they are someone you would, could, or should buy from. I'm sure (well, I'm pretty sure) that someone on Ebay has them for sale, but so far I can't deduce the wording they used for listing them. https://www.tritekelectronics.com/privacy-pol … fic-brk-ps2-2x4

A number of other vendors that had those came up on Google - all at about the same price.

I found a listing that is live, though the seller is away: https://www.ebay.com/itm/184607961976

Dear Repo Man. Thank you very much. I have tried everything so far. I have bought PS/2 converter didn't work, mouse didn't even get electric energy, tried different angles still no. Tried to brush the Comports with IPA... Tried 7 different cables. Changed BIOS settings and Comport settings. Tried 4 different mice. Can it be due to windows 95 or what I don't know what to say. But I just want this PC to work under 95. Bad thing is it is very fast and everything is working properly except the mouse.

Does the PS/2 header have voltage on the pins indicated in the chart?

I cannot say exactly but these are the detailed pictures.

This is how my boards pins look. But I cannot calculate whether the board pin outs have voltage or not since I am not equipped with any device nor with skills.

To track down the exact issue you will need to procure a basic multimeter and measure the voltage. Here is a quick video on measuring DC voltage, and the meter used is a basic one that can be purchased for less than $20.00.

https://www.youtube.com/watch?v=glVID_skJFQ

I will try this yes. But it is strange even ISA comport didn't work. I suspect something related to BIOS may trigger it. Maybe the board meant to be an industrial one but still should support mouse through comports. Meanwhile I sent an e-mail to Mitac Europe and surprisingly at this hour of the day I got a response and they will probably jump into the action to look into the issue. After many years, it is nice to see a solid company who stand firmly behind their products. I will update you guys. Appreciate all help. Once I finish the machine, it will be a great one. The Voodoo Banshee is waiting to kick off for Mitac!