If you are using an electronic KVM, it may be on the
edge of its range, or it could be bad cabling, long
cabling, or a loose connection. I found out that
electronic KVM's (especially older ones) have some
fairly well-defined limits on bandwidth. Of course,
mechanical ones do too, but for other (mechanical,
crosstalk-type) reasons. I found that the more
expensive cabling with real coaxial in it makes a big
and visible difference on longer cable runs/higher dot
frequencies.
I already made sure the cables were good. The KVM works
on the other three systems added, which are all driving
the monitor at 1600x1200 @75Hz or higher.
--
Eric Dittman
dittman(a)dittman.net
Check out the DEC Enthusiasts Club at
http://www.dittman.net/