Erratic mouse movement and a KVM switch (Win98).

Linux + Windows + KeyTronic Trackball + KVM switch = Erratic pointer behaviour in Windows.

This article describes two possible solutions to the problem of erratic mouse behaviour arising on a Windows-based computer when the computer misinterprets information arriving via a KVM switch. Neither solution is especially desirable but they are slightly better than the alternative of powering the computer off and restarting it.

Please note that this article describes a problem and solutions for a computer running Windows. There is another article that describes a possible solution for a Linux KVM/mouse problem on a SuSE Linux-based computer.

Content revision history:
Article created, summer 2004
Explantions enhanced, September 2004

Background information

Five computers were connected to a Belkin OmniView Matrix “F1D208-OSD” KVM (Keyboard Video Mouse) switch. Two of the computers were running SuSE Linux 8.1, one was running SuSE Linux 9.0, one was running Windows 2000 and one was running Windows 98SE.

The single keyboard connected to the switch was a KeyTronic “lifetime” series keyboard with trackball. Sometimes the Windows 98 machine would stop processing the trackball operations correctly and the result would be that the mouse pointer would move erratically around the screen and the computer would behave as if the trackball / mouse buttons were being pressed. This was, to say the least, annoying.

This article describes a possible fix for the computer running Windows 98 — there is another article if you want to know about the solution for the computer running SuSE Linux 9.0.

Two solutions are known for the problem described above and although both solutions are simple to implement they are also tedious and their main advantage is that they are just slightly better than the alternative of switching the computer off and on.

Solution 1: Restart Windows 98

Since the keyboard would usually continue to perform normally it should be possible to activate the Shutdown menu, then hold down the shift key and choose restart. Holding down the shift key while selecting the restart option tells Windows that it is not to do a full reboot but only to restart Windows itself — this is much faster than doing a full reboot.

Solution 2: Reinstall the mouse.

This is perhaps the better of the two methods because it is slightly faster and there is no need to shut down any tasks in progress. However, be warned that a better method is by no means an excellent method; it is still a tedious solution to an irritating problem.

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Use the keyboard to bring the control panel onto the screen. Use the tab key to highlight the icons and use the arrow keys to move the highlight to the “system” icon. Use the enter key to select the “system” icon. Once the system window has opened, use the Ctrl-PgUp and Ctrl-PgDn down keys to reveal the device manager pane. Inside the device manager pane you again use the tab and arrow keys to highlight the mouse information and, when the mouse information is highlighted, to move the focus to the “remove” button. Once the mouse has been thus deleted, simply choose the refresh option and, after a moment or two, Windows will inform you that it has found new mouse hardware and is installing the drivers for it. Once the driver is reinstalled the pointer should behave correctly — at least until next the time it goes wrong.

Avoiding the problem in the first place

The erratic pointer motion has been observed arising from two operations. Sometimes it arises on the Windows machine when using a KVM button to switch from a Linux machine. On other occasions it appears to occur spontaneously on the Win 98 machine.

However, the erratic motion has never been seen to occur after switching KVM channels when the KVM channel was switched using the hot key controls rather then the KVM front-panel buttons.

For the Belkin F1D208 OmniView the channel can be changed by pressing the following hot key combination:

Scroll Lock - Scroll Lock - <bank number> - <device number>

Where device number is between 0 and 8 inclusive and bank number depends on your installation (but for a single KVM switch will always be zero). For example, to switch to the fifth machine on bank zero:

Scroll LockScroll Lock  0 5

Sometimes the Belkin OmniView 2x8 KVM gets confused about the state of the Scroll Lock key and beeps (to show that a channel change is in progress) after only one press of the key; it can be resolved by pressing some neutral key like a shift key and then pressing Scroll Lock again. It might be necessary to press the keys with a delay of a second or two in order to get the desired effect and certainly the OmniView KVM does not seem to be happy to recognize rapid key presses.

Erratic pointer motion on a GNU/Linux system.

A similar problem of erratic pointer movement can also occur on GNU/Linux systems and a number of people have posted information to the web concerning this. There is also an article, similar to this one, about erratic mouse operation with SuSE Linux on this web site.

What, allegedly, is the cause.

Various web postings, including manufacturers' technical pages, claim that the problem occurs because of a mismatch between the mouse drivers on the systems connected to the KVM switch. This strikes me as being a feeble excuse since a KVM switch is supposed to be transparent to the systems connected to it. It seems rather foolish, or at least unrealistically optimistic, to expect a KVM switch user to install the same operating system and drivers onto every machine just so that the KVM switch can perform its supposedly transparent task correctly. Consequently I am inclined to regard the problem as a manifestation of incompetence on the part of the KVM switch manufacturers.

Nonetheless, bearing the above mentioned explanation in mind, it might be that you will be able to improve matters with your installation by trying different drivers for your pointing devices and, if you have machines that all have the same operating system, possibly by ensuring that all machines are using standard and identical drivers for their pointing device. Again, a web search will probably provide you with useful information. Good luck!

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