4 Computers, 1 Screen. Way expensive. (About $3,800 USD Retail).
http://www.nti1.ca/quad-splitter.html
http://www.nti1.ca/images/splitmux-dvi-4.jpg
http://www.nti1.ca/images/app-splitmux-dvi-4.gif
Why buy this over 4 screens? No idea. It doesn't even do dual link DVI. Display Port where are you???
"The Quad Screen Splitter allows you to simultaneously display and monitor video signals from four different computers and/or video sources on a single screen. Additionally, the SPLITMUX can switch one of the four attached computers to a shared keyboard and mouse for operation. - Quad, Picture in Picture, and Full Screen display modes.
- Independent video in to video out resolution.
- Supports up to 1600x1200 video resolution.
- Accepts analog and digital video signals simultaneously.
- Connect analog and digital devices to the splitter, and display images on a digital or analog monitor."