Typical X servers provide multi-head support for multiple displays attached to the same machine. When Xinerama is in use, these multiple displays are presented to the user as a single unified screen.
Xdmx is proxy X server that provides multi-head support for multiple displays attached to different machines (each of which is running a typical X server). When Xinerama is used with Xdmx, the multiple displays on multiple machines are presented to the user as a single unified screen.
A simple application for Xdmx would be to provide multi-head support using two desktop machines, each of which has a single display device attached to it.
A complex application for Xdmx would be to unify a 4 by 4 grid of 1280x1024 displays (each attached to one of 16 computers) into a unified 5120x4096 display.
Xdmx was developed and run under Linux (ia32 and x86_64) and has been tested with SGI Irix.
Current Open Source multihead solutions are limited to a single physical machine. A single X server controls multiple display devices, which can be arranged as independent heads or unified into a single desktop. These solutions are limited to the number of physical devices that can co-exist in a single machine (e.g., due to the number of AGP/PCI slots available for graphics cards). Thus, large tiled displays are not currently possible. This limitation will be solved by eliminating the requirement that the display devices reside in the same physical machine. This will be accomplished by developing a front-end proxy X server that will control multiple back-end X servers that make up the large display. These X servers can either run on the same or separate machines.