Xdmx

Distributed Multihead X solved a problem graphics cards couldn't: driving a display wall with more monitors than one machine has outputs. Xdmx talks to no hardware at all. It connects as a client to ordinary X servers on other machines, one per screen, and presents their sum as one large logical surface to the programs that connect to it. Drawing requests are translated and relayed to the right back-end server, much like Xnest but spread out, and OpenGL went through a proxy of its own.

The code came from Red Hat and was merged into X.Org in 2004. It saw use at institutions with video walls and the occasional classroom, but performance was what it was: every pixel crossed the network twice. Once large displays became cheap and a single card could drive four of them, the need evaporated, and X.Org removed Xdmx from the server in 2021.