The driver needs the same hardware modification what was made by you or Anonymous Coward.
It include installation of the inverter circuit and connection Irg12.
The driver adds support PS/2 mouse without need to modify the BIOS.
It contains TSR module and the installation module.
TSR module include int 15h handler (services C2h and C1h) and int 74h handler.
The installation module does the following:
- check, whether there is already support for the mouse,
- adds mouse to the equipment list, at 40:10h address,
- unmasks Irq12 PIC,
- changes interrupt vectors 15h and 74h to its own.
I have tested with Award BIOS 4.50 (also it was tested with modified BIOS) and Ami BIOS 2.11 (1993).
386DX-40 motherboard is M326 V5.2 model. I did the same modification KBC, as you with your DTK PKM-0033S.
I have no NT4 driver. I suppose it is not needed.
You just need to enable the Irq12 at PIC and add mouse to the equipment list.
Everything else is already included in OS.
Added 26/01/18.
Last version of the driver, rev.1.0.2c, is here:
https://yadi.sk/d/5ge32bgv3RoUHs