Ps/2 KVM used to be good
but now in days it is becoming harder and harder to use those
a USB KVM is definitely the way to go
the Linksys one i mentioned has Both USB and PS2
so you are safe on that area, nothing to worry about you've got 100% support for old and new hardwares.
the only thing missing from that great KVM is Sound and MIC 😛
but heck you can't get anything perfect these days, and the Linksys USB+PS2 KVM is the best that you can find.
Now if i can only get the 8 port version of it then it'll be great
even the 4 port version was hard to find
i was forced to use several 2 ports on 2 ports on 2 ports on 2 ports to control all my rigs (cascade flow 6 > 3 > 2 > 1)
it's kinda cool in a way, it allowed me to be more flexible and be dualing keyb / mouse 2+ rig at the same time, rather than limited to just 1 keyb/mouse as it would have been if i was using a 4port or 8port
the only trouble was to memorize at any given time and moment which switch i'm on 😀