[gentoo-user] KVM problems - anyone know _why_ it happens?

[Mark Knecht]

I've seen reports for years about folks having problems with some KVMs
under Linux. I've never personally had one myself. However I've been
helping a Windows friend break his Redmond addiction over the last few
months using Gentoo. He has a nice 3 monitor KDE-based system that's
been working fine but there was one monitor that refused to set up
with the right resolution. We left it alone for a long time as it was
usable but finally yesterday got together to figure out what was
happening. From the title it should be clear that the problem was a
KVM hooked to that one monitor. Removing the KVM completely solved the
problem.

Now, what I'm wondering is why this same video card/KVM/monitor
combination which apparently worked in Windows should have any
problems in Linux? Anyone know why?

In the spirit of full discloser I don't really know that this
_specific_ video card was tested in Windows, but he owns multiple
NVidia 8400GS cards and it's my understanding that other 8400GS cards
did work with this KVM & monitor, so unless it's this specific card
having a defect, or even being just a bit weak in some way, it would
seem to be the insertion of the KVM itself that upset things.

Looking at the monitor's specs/requirements for running the higher
resolutions it uses, as should not be a surprise, higher frequencies
to do higher resolutions. If the KVM was filtering those a bit then
it's possible things wouldn't work, but that doesn't explain why it
did work in Windows.

Basically, I looked around in Google for anyone that had real info
about why this problem occurs, couldn't find any that made sense, and
am wondering how to choose a KVM that's going to work out of the box
short of asking for model numbers, etc.

Cheers,
Mark