naujoks wrote on 2024-02-07, 16:41:

I have a 486 33Mhz on a Biostar MB-1433PA-CH board and I'm having trouble with the mouse under DOS. The board needs an ISA contr […]
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I have a 486 33Mhz on a Biostar MB-1433PA-CH board and I'm having trouble with the mouse under DOS.
The board needs an ISA controller card for serial ports (it has no PS/2 ports).
The mouse works perfectly under Win3.1 and Win95, but is erratic under all DOS applications such as games. It seems to generate random mouse movements and clicks on its own.
The only other card I have on the board is a SB 16 (on IRQ 5).
I can set the IRQs of COM1/COM2 manually on the controller card and I have tried all possible IRQs (3, 4, 7, 9) but nothing makes a difference.
For the driver under DOS I'm using CTMOUSE 1.9.

Any idea what the problem might be?

You don't have a graphics card? Amazing!

Well yes I do, in fact I tried two different ones.

I asked, because you wrote:
"The board needs an ISA controller card for serial ports (it has no PS/2 ports).
.....
The only other card I have on the board is a SB 16 (on IRQ 5)."
=> So you wrote, you have only the controller and the SB 16, that means no video card.
OK, now a more serious question:
Is the problem the same, when you remove the SB 16, so keep only the controller and the video card?
And I would suggest to use com1 => IRQ4 for the serial mouse.

I found the mouse driver for my particular mouse (Genius Mouse One) and used it instead of ctmouse. It's working now. Strange. But ok.