[gpm] Weird behaviour

Geoff Martin gpm@pfw.demon.co.uk
Thu Feb 5 15:13:14 CET 2009

On Sun, 11 Jan 2009 18:29:55 +0000
Geoff Martin <gpm@pfw.demon.co.uk> wrote:

> Dear Chaps,
> I wonder if you can help me with a particularly nasty mouse
> infestation... I'm running Linux with glibc 2.5.1 and using
> gpm 1.20.1. I have a PS/2 mouse, as provided by a video switch. I run
> gpm with:
>    # gpm -m /dev/input/mouse0 -t ps2
> and as I move the mouse, the pointer moves wildly in random
> directions, makes selections and pastes them. In short, it looks like
> gpm doesn't understand the protocol coming out of the device.

This is just a follow-up for those who experience the same problem as
me. It turns out that the video switch (a vintage BlackBox ServSwitch
Ultra) is a bit mean with the voltages, so that it works with some
motherboards and not others! I now use a PS/2 to USB dongle and all is

What had me going was the fact that the keyboard signals are fine; the
only symptom is corrupted mouse data. I figure the 8042-like circuits
in the chipsets reject some bytes because they see parity errors (or
some such).

It seems fine with Intel and Supermicro boards, but not with GigaByte.
Now you know.



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