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

[Michael Mol <mikemol@gmail.com>]

On Sun, Jan 22, 2012 at 10:54 AM, Mark Knecht <markknecht@gmail.com> wrote:
> 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.

I assume these are VGA displays?

I've noticed that the CRTs attached to my Win7 box at work don't get
configured for the highest refresh rate unless I force it. Also, I've
noticed it decide that '1280x1024' is the 'recommended' resolution for
my displays, though they'll do 1600x1200@60Hz.

It could just be a matter of Windows using 75Hz instead of 85Hz, or
60Hz instead of 75Hz.


-- 
:wq