KVM switch problem

Tim ignored_mailbox at yahoo.com.au
Wed Jan 31 08:39:19 UTC 2007


Tim:
>> Watching this thread, and the woes that a friend has gone through with a
>> KVM on his Windows boxes, I begin to wonder if the problem is down to a
>> lack of power to run the devices.

David G. Miller:
> Had the same thought when trying to correct mouse weirdnesses with my 
> Belkin KVM.  I bought one of their auxiliary power supplies and it
> made no difference at all. 

A friend of mine has a crap-brand "Laser" one.  He had a USB one, but
that failed all over the place (you'd have things acting like there is
no keyboard or mouse, it'd lock up, the computers would lock up, even
the LED tallies would only light dimly on some PCs), and he'd have to go
through unplugging each thing in turn and replugging and rebooting...

He swapped it for a PS/2 one, and got away from most of those problems,
though they still occasionally occur.  It still has LED tallies that
look a bit too dim, in some cases, and the KVM locking up, so that leads
to the thought about the thing lacking power.  And occasionally,
plugging in another PC, will lock things up (often everything).

> The weirdness I ran into is my mouse goes "nuts" when I change systems
> using the KVM.  It jumps all over the place, signals various "button 
> down" events, etc.  The solution seems to be to just unplug the mouse 
> from the KVM whenever I switch systems and plug it back in after the 
> switch.  Weird.  The keyboard and monitor switch with no problems. 

I've seen that happen with Linux ever since I started using it back in
the Red Hat 6.0 Linux days, and it still does occasionlly, with mice and
keyboards plugged directly into the PCs.  With various different mice
and keyboards.  On various different motherboards, too.  USB mice seem
less prone to it, mine will occasionally do a wild dart away, but I
haven't seen it fake a click for a long time.  It's almost like
someone's made a right mess of coding the mouse accelleration functions.

e.g. Wild mouse behaviour, as you described, and similar wild keyboard
behaviour (keys jamming down and repeating until you smack a handful of
other keys down, and keys not being noticed being pressed).

I've come to the conclusion that mouse and keyboard interfacing on Linux
has problems all of its own.





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