Erratic mouse operation and a KVM switch (Linux).

SuSE 9.2 + SuSE 10.0 + KeyTronic Trackball + Belkin KVM switch = Erratic pointer behaviour.

The author has encountered various problems when using a KVM switch with computers operating with one or another version of SuSE GNU/Linux. This article describes one such scenario and its resolution.

Content revision history:
Article first written, 20th February 2006

Background information

Two computers were connected to a Belkin four way KVM switch.One computer was running SuSE GNU/Linux 9.2 and the other was running with SuSE GNU/Linux 10.0.Both computers had been performing correctly when operated in isolation but when they were connected to the KVM switch they both exhibited the same malady.

mouse by bath plug hole
Before you try a complicated technical solution, consider whether your mouse just needs a rigorous cleaning in the bath.

The single keyboard connected to the switch was a KeyTronic “lifetime” series keyboard with trackball.The screen pointer associated with the trackball did not follow the trackball motion smoothly and from time to time the computer would act as if one or more of the trackball buttons had been pressed.With these symptoms the graphical user interface of each computer was effectively unusable.


The action take to effect a cure

First the XFree86 configuration was adjusted.On these systems, the XFree86 configuration file can be found at: /etc/X11/XFree86.conf

Within this configuration file is a section with parameters and options for the pointing device.The contents of this section are shown below:

Section "InputDevice"
  Driver       "mouse"
  Identifier   "Mouse[1]"
  Option       "Device" "/dev/mouse"
  Option       "Emulate3Buttons" "on"
  Option       "Name" "Autodetection"
#  Option       "Protocol" "ps/2"
  Option       "Protocol" "auto"
  Option       "Vendor" "Sysp"

As can be seen from the commented-out line, the protocol was changed from “PS/2” to “auto”.Thereafter the mouse performed as it should.This change was made only because it had been effective with a similar problem previously but, in this case, the change made no difference. A further change was therefore made, this time to the boot parameters in the grub configuration file.

This file is found at: /boot/grub/menu.lst

The text "psmouse.proto=imps" was added to the list of kernal parameters, as seen below:

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Erratic pointer motion on a Linux machine connected to a KVM switch.

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