I ended up doing a lot of research into why my windows won't stay where I put them when I switch computers. It turns out that the DisplayPort specification requires sending a monitor-off signal. You absolutely must use HDMI if you don't want this problem. I was able to use other KVM and HDMI DisplayPort cables without any problems. If that's not your main concern, this is a fantastic KVM. It had no trouble moving the 4k and WHD display. Switching was quick, it took me minimal effort to get my gaming keyboard and mouse up and running.
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