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KVM Switch Automatically Changes Screen Resolution

 1:33 pm on Apr 25, 2007 (gmt 0)

I added a KVM switch to control two PCs.

As soon as I boot up when the KVM switch is attached, the resolution changes to 800 x 600. Unplugging the KVM switch and connecting direct to the keyboard/mouse/monitor, and it reverts back to the original settings.

Why does this happen?

Obviously, I have changed the resolution back to the original while the KVM switch is attached.



 11:14 am on Apr 26, 2007 (gmt 0)

What is a KVM switch?


 2:22 pm on Apr 26, 2007 (gmt 0)

Keyboard Video Mouse switch enables control of multiple computers from a single keyboard, mouse and screen.


Strange thing is, I have never had the problem of the resolution changing on a hardware KVM switch before.


 1:16 am on Apr 27, 2007 (gmt 0)

Depends on the relationship between the switch and the OS (read: drivers). See if there isn't a driver update for your OS.


 3:10 pm on Apr 27, 2007 (gmt 0)

Sounds like the KVM is either not passing-back or not caching DDC, and your OS is configured to use DDC to set the monitor resolution.

DDC is a signaling standard that allows your monitor to tell the computer it's resolution and other characteristics.

I would first make sure that when you reboot, you've switched the KVM to that computer. If that doesn't work, you'll have to configure your OS to explicitly set the resolution, rather than using DDC.


 6:03 pm on Apr 27, 2007 (gmt 0)

Thanks for the tips.

The KVM is switched to that machine, and it has all the latest drivers. Both machines are using XP Pro SP2 and the second machine works just fine.

But then, these things happen, and no one machine seems to perform the same. :/


 10:13 pm on Apr 27, 2007 (gmt 0)

Have you installed a specific driver for your monitor, or are you using one of the "generic" drivers? I'd suggest using a specific driver, if one is available. Otherwise, at least make sure you have chosen your monitor from the list of supported monitors. Your video adapter driver may also have a setting to use or ignore DDC.

It sure looks to me like the problem is DDC, since it works fine when you hook-up the monitor directly. The KVM is not sending the DDC to the video adapter.

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