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evildragon
September 21st, 2013, 06:02 PM
I'm finding that my mouse port on my model 25 acts funny a lot of times.

If I am moving the mouse and hitting keys very fast (like in a video game for example), the mouse immediately starts freaking out, flying all over the place and clicking random things. This happens on any OS, any mouse driver, any game, and the fix is always the same. Close the game, and relaunch it. It does this on Windows 3.0 too.

Early PS/2 port implementation issues? Should I just get a serial port mouse?

Chuck(G)
September 21st, 2013, 06:21 PM
Just curious--have you tried another mouse?

evildragon
September 21st, 2013, 06:32 PM
Just curious--have you tried another mouse?
Yea, I should have mentioned that. I tried every mouse I had, even IBM PS/2 originals.

Chuck(G)
September 21st, 2013, 07:07 PM
Before I resorted to extreme measures, I'd check the connector on the motherboard--you could have a bad solder connection that's creating an intermittent.

But yeah, there's always the serial mouse approach...

evildragon
September 21st, 2013, 07:37 PM
Before I resorted to extreme measures, I'd check the connector on the motherboard--you could have a bad solder connection that's creating an intermittent.

But yeah, there's always the serial mouse approach...

Just got done checking since it was already apart. Reflowed the solder as a test. Still didn't fix it. It's only when I'm pressing keys on the keyboard. I tried the other PS/2 port (sine on a model 25 the two PS/2 ports aren't actually labeled mouse or keyboard, in fact you can have two keyboards if you desire), and still, same thing.

Chuck(G)
September 21st, 2013, 09:33 PM
Is this something that just started happening or has it been this way all along? Could be a firmware glitch in the keyboard controller.

evildragon
September 21st, 2013, 10:10 PM
Is this something that just started happening or has it been this way all along? Could be a firmware glitch in the keyboard controller.

It's always done it as long as I remember. Different model 25 motherboard, same thing. I didn't know if there was a fix for it or what.. Serial mouse is starting to look good but I don't think I have the 25 to 9-pin adapters.

Caluser2000
September 21st, 2013, 10:22 PM
Does swapping the mouse and keyboard to the other port have any effect?

Chuck(G)
September 21st, 2013, 10:40 PM
It's always done it as long as I remember. Different model 25 motherboard, same thing. I didn't know if there was a fix for it or what.. Serial mouse is starting to look good but I don't think I have the 25 to 9-pin adapters.

They're still everywhere--Amazon, eBay, Cables2Go,... And not expensive.

evildragon
September 21st, 2013, 11:49 PM
Does swapping the mouse and keyboard to the other port have any effect?

As per:

I tried the other PS/2 port

Sadly no. Doesn't help.

RJBJR
September 22nd, 2013, 06:21 AM
Does the PS/2 Model 25 have the CBIOS (compatibility) and ABIOS (advanced) BIOS? If it does then OS/2 may be worth a try.
Much easier to try a serial mouse first.

pl212
May 16th, 2014, 08:46 AM
I've encountered similar problems with an original IBM Mouse on the PS/2 Model 25 (original 8086 model). Sierra games seem fine (KQIV) but Loom makes the mouse go crazy. Seems to be correlated with pressing numeric keypad keys simultaneously with, or around the same time as, using the mouse.

Possible evidence this was a problem with all 8086, non-MCA PS/2 Models: special instructions in this manual...

http://mocagh.org/ea/centurion-refcard.pdf

PS/2 model 25 and 30 users: For best results, connect your mouse to the serial port.

(there are some other special instructions in that manual but I think they relate to the assumption that the Model 25 and 30 used the SpaceSaver keyboard, which had no numeric keypad. Not exactly true for most Model 30s, more likely for the 25's.)

pl212
May 21st, 2014, 09:11 AM
From Louis Ohland's site (http://ps-2.kev009.com/ohlandl/parts/mouse.html) -


One peculiarity of the PS/2 mouse is that the packet format it employs does not include a clock bit as the Microsoft packet does. Furthermore, because the same system board controller is used to decode data coming from the mouse and the keyboard simultaneously, programs that use both the mouse and keyboard on the PS/2 sometimes experience data-overman conditions that cause the mouse driver to lose synchronicity with the mouse. If there were a clock bit, timing could be reestablished and the overrun condition could be defeated. Without the clock bit, application programmers have been forced to resort to several ad hoc means of maintaining the integrity of the
information flowing to the mouse driver. Some of these methods are more effective than others. If your mouse goes haywire or simply stops working when you run certain application programs on a PS/2 (especially older programs), it's probably for this reason.

sean1978
September 6th, 2015, 09:50 AM
SO did you ever figure this problem out? I'm having a similar issue with my model 25.

krebizfan
September 6th, 2015, 10:48 AM
You have two options:
Find a revised version of software that corrects for the mistakes IBM made in the design of the PS/2 mouse interface or switch to a serial mouse.

pl212
September 7th, 2015, 09:31 AM
One option would be to grab a copy of mouse.com from a much later version of IBM's PC-DOS (say 5.0) and see if that helps.