At least two computers with separate monitors.The software allows you to share a single keyboard and mouse between Windows, Mac, and Linux computers. Synergy is an easy to set up open source application that allows you to share a keyboard and mouse between multiple networked computers. Sure, I could use a KVM, but I didn't have one handy, so how could I lose one keyboard/mouse combo? I didn't think it was going to be possible, until I found an incredibly simple and free solution called Synergy. I have two keyboards and two mice on my desk, and switching back and forth between those keyboards caused me to have all sorts of back problems. There are three monitors on my desk, two of which are attached to one computer and one monitor that is attached to another computer.