When a serial mouse refuses to work, there are usually two reasons for this - insufficient -12/+12V voltage on the motherboard or the wrong type of serial port cable. If the COM port header zigzags in relation to DE9 plug's pinout, the cable needs to be split in half at the end where it is soldered to the COM port plug. In newer computers (Pentium era+) it was usually the other way around - the port connector pins were arranged in a sequential manner and the cable was soldered in a zigzag pattern. Make sure that the cable type is correct, ground is a good indicator to determine that, it has to be on pin 5 of DE9 plug.

More detailed info on this matter can be found here.

The 6-pin header next to the KB connector should be for the PS/2, but it will likely have a non-standard pinout as other MBs typically have a 5-pin header with a missing key pin. Trace its pinout from the absent PS/2 connector's solder pads, it will consist only of +5V, GND, data and clock signals.

*Note, from the COM port pinout provided, it appears that you are using an older "split in half" type of cable, which was commonly used in computers prior to the PCI era.

SSTV2 wrote on 2025-09-19, 00:13:

When a serial mouse refuses to work, there are usually two reasons for this - insufficient -12/+12V voltage on the motherboard o […]
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When a serial mouse refuses to work, there are usually two reasons for this - insufficient -12/+12V voltage on the motherboard or the wrong type of serial port cable. If the COM port header zigzags in relation to DE9 plug's pinout, the cable needs to be split in half at the end where it is soldered to the COM port plug. In newer computers (Pentium era+) it was usually the other way around - the port connector pins were arranged in a sequential manner and the cable was soldered in a zigzag pattern. Make sure that the cable type is correct, ground is a good indicator to determine that, it has to be on pin 5 of DE9 plug.

More detailed info on this matter can be found here.

The 6-pin header next to the KB connector should be for the PS/2, but it will likely have a non-standard pinout as other MBs typically have a 5-pin header with a missing key pin. Trace its pinout from the absent PS/2 connector's solder pads, it will consist only of +5V, GND, data and clock signals.

*Note, from the COM port pinout provided, it appears that you are using an older "split in half" type of cable, which was commonly used in computers prior to the PCI era.

Thanks for reply!! finally serial mouse is working, was a "software" problem, it seems someone flash a bad bios, maybe from similar board, and some stuff was not working well. After flash correct bios, serial ports start working fine!! the best is I found a working MrBIOS! amazing

About PS/2, y have 6 pins

From left to right, pin 1 and 4 give me 5v, pin 3 is GND, I think PS/2 can be, 2 to 6, but i made every combination from pin 2, 5 and 6 with clock and data, without luck... out of ideas!

Did not expect that to be an issue 😕

A 6-pin header will likely fit this pinout, but you should verify that using a DM. You can see two traces running across J3 pads, leftmost connects to pin 1 (data), and rightmost connects to pin 5 (clock).

SSTV2 wrote on 2025-09-19, 17:46:

Did not expect that to be an issue 😕

A 6-pin header will likely fit this pinout, but you should verify that using a DM. You can see two traces running across J3 pads, leftmost connects to pin 1 (data), and rightmost connects to pin 5 (clock).

Thanks man! this pinout was corect, i did not check pin 1, because the 5v, thanks a lot, i have a working PS/2 Port right now!!

I have run into that issue too--motherboard manufacturer made similar boards with same chipset and different Super I/O, and previous owner flashed the wrong Super I/O. Weird things happened like the parallel port always being at 278h no matter what was set in the BIOS, since it couldn't configure it properly.

theelf wrote on 2025-09-19, 18:09:

Thanks man! this pinout was corect, i did not check pin 1, because the 5v, thanks a lot, i have a working PS/2 Port right now!!

Well done 👍

SSTV2 wrote on 2025-09-19, 20:05:

theelf wrote on 2025-09-19, 18:09:

Thanks man! this pinout was corect, i did not check pin 1, because the 5v, thanks a lot, i have a working PS/2 Port right now!!

Well done 👍

Thanks for your help!

jakethompson1 yes, for sure are some revisions of board, and IO chipset or some components are different, because like you say, some of bios have parallel at 278, even if you check in retroweb, there is 2 MrBIOS for this board, one have paralel on 378 the other on 278, but on both serial works fine