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I recently installed a PS/2 KVM switch that is connecting two Ubuntu servers and a Windows 2008 server. It worked fine with the Ubuntu boxes, but on the Windows box whenever I try to move the mouse the pointer jumps all over the screen and acts as though the buttons and scroll wheel have been clicked/moved in a seemingly random pattern.

I tried shutting down all of the boxes and disconnecting both Ubuntu boxes from the KVM and resetting the KVM, but when I rebooted the Windows server the problem persisted. If I plug the mouse directly into the Windows server, it works normally, but if I plug it back into the KVM switch the problem returns. Does anyone know of any way of stopping this?

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Windows 2008 servers and Windows 7 share the same core for monitoring the status of connected devices - the OS will continuously check/communicate to all the I/O devices (including keyboard, mouse, audio devices and display monitor...etc.)

The issue you experienced should be the PS/2 protocol /emulation with your KVM switch. I suggested to use USB KVM switch with USB DDM (Device Dynamic Mapping) technology.


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It is a problem with the COM port. You are probably using a device on a COM port that windows detects as a mouse (COM1 default). Disable the COM port mouse rather than uninstalling and restarting the system.

According to TalTech:

Since the release of Windows XP and NT, whenever Windows boots up, it searches for a serial mouse on any built in COM ports on your PC. The way that it does this is to look for any data at all coming in the serial port at boot time. If Windows sees data coming in a COM port at boot time, it loads a mouse driver for that COM port. The consequences of this are that the COM port becomes unavailable to any other program, and that any data received through the COM port could potentially be interpreted as mouse movements and clicks causing your PC’s mouse cursor to jump erratically and uncontrollably. It can even cause your PC to crash.

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Thats an interesting theory, but backing it up with sources would seriously improve your answer. – Journeyman Geek Mar 7 '13 at 13:38
This was definitely not it. I did not have anything plugged into the COM port, and the mouse would only move erratically when the actual mouse was moving. – murgatroid99 Mar 7 '13 at 14:56

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