Accelerated-X is a proprietary port of the X Window System

X Window System

The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...

 to Intel x86 machines.

History

The Accelerated-X server is built on top of the X386

X386

X386 was the first implementation of the X Window System for IBM PC compatible computers. It ran on systems with Intel 386 or later processors, running Unix System V-based operating systems, and supported a variety of VGA-compatible graphics cards. X386 was created by Thomas Roell while at...

 X server that was created by Thomas Roell for X11 Release 5. He founded a company in Colorado

Colorado

Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

 named Xi Graphics which still provides the Accelerated-X server.

The XFree86

XFree86

XFree86 is an implementation of the X Window System. It was originally written for Unix-like operating systems on IBM PC compatibles and is now available for many other operating systems and platforms. It is free and open source software under the XFree86 License version 1.1. It is developed by the...

 project was created as a free alternative to what became the Accelerated-X server.

Features

Accelerated-X server provides an "overlay mode" on several graphics cards which allows running ancient, 256 color mode-only Unix alongside more modern applications on truecolor 24 bit displays.

It used to provide much better driver support (hardware acceleration, 3D and compatibility, especially on integrated graphics) than XFree86, at a time when the major graphics chipset vendors were not supporting Linux officially.