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Serial mouse troubles with 486 board

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First post, by einr

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So I'm working on building my 486, and it's getting to be a lot like whack-a-mole... Pound down one problem, another pops up on the other side of the board 🤣

Quick backstory: found a complete 486 DX4/100 at a flea market. Everything worked fine except the motherboard which was dead. Bought a new board off eBay. New board (M Technology R407E/V with AMIBIOS) came with RAM and a DX-33 CPU. It booted fine the way it was. Tried putting the new board into the old case. New board has different layout; 72-pin RAM slots blocked by 5,25" drive cage. Order new 30-pin RAM. Install motherboard in case, replace DX33 with DX4, install 16 megs of 30-pin RAM. Connect all the buttons and LEDs. Boot it up, everything eventually works fine... Except!

After putting the motherboard into the case, installing new RAM, and switching around the cards a bit, now my mouse doesn't work.

The mouse is a serial Microsoft mouse that definitely worked with the same motherboard and I/O ISA card before I put it in the case. While working on the board I might have switched around the positions of the ISA cards etc. Don't really remember how it was.

So: I plug the mouse into COM1 on the multi I/O card. MOUSE.COM detects it fine, MSD.EXE shows correct-looking mouse info, and the mouse pointer shows up:

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However, mouse is immobile. Can't move the pointer. So I check the IRQ settings and this looks really weird:

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Why would it show IRQ 0 as being handled by the mouse driver? Isn't this wrong? What's going on here? What should I do? Honestly, don't know where to even start with troubleshooting this. Help appreciated 😖

Reply 1 of 6, by Tommaso72

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It looks to me your serial mouse is on IRQ 4, but I could be wrong. The confusing part is it comes up in two places, so good question. I would think IRQ 4, but may be someone more knowledgeable can answer why it shows up in too places. Sorry I can't be of any real help.

Tommaso

Reply 2 of 6, by TheMobRules

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Maybe you could try a different mouse driver? It seems that the MOUSE.COM you're using also registered itself to handle the system timer interrupt (IRQ 0)... very strange. What does the diagnostic program show in IRQ0 if you do not load any mouse driver?

Reply 3 of 6, by Jepael

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Check that you have the correct motherboard to backpanel connector cable. There are at least two different kinds of those. Maybe you have the wrong one and some pins don't match.

Even if you have the correct cable, your serial port might still be broken. Mouse usually needs two or three output pins from PC for powering all subsystems (controller IC, optical encoder LEDs). Have you tried another serial port, or serial connection to another machine? Serial loopback? Any terminal program to receive data from mouse?

Clearly the mouse gets detected, so at least the mouse controller IC gets power and it sends back something recognizable to the mouse driver (letter 'M' for microsoft protocol mouse).

Also, check that your mouse is set to Microsoft protocol if there is a switch.

Edit: Oh, it was an ISA serial adapter and it was working before. So most of this does not apply then.

Reply 4 of 6, by Jo22

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No idea whether this helpful or not, but perhaps it helps to rearrange the IRQs for the serial ports.
http://www.pcguide.com/ref/mbsys/res/irq/numIRQ2-c.html
(seee last paragraph)

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Reply 6 of 6, by nforce4max

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einr wrote:

Thanks for all the replies!

Turns out all I needed to do was re-seat the I/O controller. That's a little embarrassing. Sorry. 😊

Now to figure out why the floppy drive won't play along...

Don't feel bad 🤣 this is common with such hardware.

On a far away planet reading your posts in the year 10,191.

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