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New KVM Switch, May 2009

My Mac Pro and Linux machine now share a single monitor (Dell 2407 24" flatscreen LCD monitor) and the Mac-Pro keyboard and mouse (both USB). This two-port sharing is implemented by a Belkin F1DG102D ``Flip'' DVI-D KVM Switch. I love this switch because all you need on your desk is the remote button, which has a small LED dot that is yellow for one computer and green for the other. The switch itself has no UI and can lie on the floor near the computer towers. (It's actually hard to do otherwise because one of the two monitor cables built into the switch is only about two and a half feet long.) In other words, the switch looks more like a cable Y-adaptor than a piece of gear--nicely done.

Previously I had a Belkin OmniView two-port KVM switch (for analog VGA and PS2 mice/keyboards), and it was a solid performer. I love it when a piece of hardware functions for years with no trouble whatsoever until it becomes obsolete (at least in my current setup--I hope to find a good home for it somewhere else).

The Mac Pro displayed immediately, which makes sense because it was previously going into the digital input (DVI-D) of the monitor, so its display settings were already compatible. The Linux box, however, had previously been going into the analog monitor input (VGA), and its display settings turned out not to be compatible with the digital monitor input--the screen was simply black, as if there were no signal at all. I luckily solved this problem on the first try by reverting to the standard VESA driver:

In /etc/X11/xorg.conf:

...

Section "Device"
        Identifier  "VideocardVesa"
        Driver      "vesa"
EndSection

...

Section "Screen"
        Identifier "Screen0"
# 	(previous setting using Driver "radeon"):
#       Device     "Videocard0" 
# 	(new setting selecting the VESA Driver):
        Device     "VideocardVesa"
        Monitor    "Monitor0"
        DefaultDepth     24
        SubSection "Display"
                Viewport   0 0
                Depth     24
# 	(previous setting using Driver "radeon"):
#               Modes    "1920x1200" "1600x1200" "1280x1024" "1024x768"
# 	(I left out the Modes line in order to let it autoselect.)
        EndSubSection
EndSection

The autoselected resolution was 1600 x 1200 at ``0 Hz'' (which I presume lets the monitor choose the refresh rate).

The Mac Pro USB mouse immediately worked fine for the Linux box as well as the Mac Pro. Switching back and forth seems to cause no problems.

The only loser is Linux trying to use the Mac Pro keyboard via the KVM switch. The two problems so far are

  1. Caps-lock behaves like caps lock instead of Ctrl, as I specify in my layout options [Fedora 10 only -- problem gone in Fedora 11]
  2. The emacs meta key is mapped to the Option key instead of the Command key
If I change my keyboard type in (Fedora 10) System / Preferences / Hardware / Keyboard / Layouts, the caps lock key gets fixed temporarily. Unfortunately, I have to do this every time I switch from Mac to Linux. A cheesy workaround is to leave the Keyboard Layout Options window open, and after switching to linux, change something and change it back. I originally changed it from ``Microsoft / Microsoft Natural Keyboard'' (my previous Linux keyboard) to ``Apple / Macintosh'' (or ``Apple / Apple''). Upon further experience, it doesn't appear that changing the keyboard type helped at all, only the fact that I changed the type from anything to anything else.

Red Hat declares KVM switches to be officially unsupported (see
https://bugzilla.redhat.com/show_bug.cgi?id=kvm), so there is no point trying to report the bug against Fedora 10. In any case, it looks like an X11-Gnome interaction bug to me.

For lots of useful related info, see https://bugzilla.redhat.com/show_bug.cgi?id=446684

My workaround is to toggle my Keyboard Layout Options between

 options = [ctrl	ctrl:nocaps]
and
 options = [ctrl	ctrl:ctrl_ac]
(I go back and forth between these in the Keyboard Layout Options panel to fix the caps-lock problem after switching the KVM to Linux.)

Note that

gconftool-2 --type string -s /desktop/gnome/peripherals/keyboard/kbd/options 
  "[ctrl ctrl:nocaps]"
does not work. While it does set the options, caps lock is still caps lock. Only making a change in the GUI has any effect.

Ironically, using ssh -X to the Linux machine from the Mac works great. Caps lock does the right thing, and even emacs works properly using the Command key for meta. I suppose I don't normally need the KVM switch after all.

I'm going to limp along with these keyboard problems for a while before giving up and going back to using a separate, directly connected keyboard for the Linux machine. It fortunately seems to be ok to use my PS2 keyboard (a Microsoft Natural Keyboard) and Mac Pro USB keyboard hooked up at the same time. However, I find it difficult to switch between the Natural keyboard and the Mac Pro keyboard due to the very different physical layouts.


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``My Computers'', by Julius O. Smith III, Web document.
Copyright © 2014-03-25 by Julius O. Smith III
Center for Computer Research in Music and Acoustics (CCRMA),   Stanford University
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