XGA, the Extended Graphics Array is an IBM display standard introduced in 1990. Today, it is best known as a synonym for the 1024×768 display resolution, but the official definition is broader than that. It was not a new and improved replacement for Super VGA, but rather became one particular subset of the broad range of capabilities covered under the "Super VGA" umbrella.
The initial version of XGA expanded upon IBM's VGA (Video Graphics Array), adding support for two resolutions:
- 640×480 pixels with high colour (16 bits per pixel, i.e. 65,536 colors).
- 1024×768 with a palette of 256 colours (8 bits per pixel)
Like its predecessor (the IBM 8514), XGA offered fixed function hardware acceleration to offload processing of 2D drawing tasks. XGA and 8514 could offload line-draw, bitmap-copy (bitblt), and color-fill operations from the host CPU. XGA's acceleration was faster than 8514's, and more comprehensive in that it supported more drawing primitives and XGA's 16 bits per pixel (65,536 color) display-mode.
XGA-2 added true-color mode for 640×480, 1024×768 support for high colour and higher refresh rates, and improved accelerator performance. All XGA modes have a 4:3 aspect ratio rounded to 8 pixels.
XGA should not be confused with VESA's EVGA (Extended Video Graphics Array) that was released at a similar time.
Clone hardware
XGA hardware was not cloned as extensively as VGA hardware. Nevertheless, at least one graphics company made several XGA-compatible chips, the IIT AGX.
See also