Extended Graphics Array XGA

Historia

he Extended Graphics Array (XGA) is an IBM display standard introduced in 1990. Later it became the most common appellation of the 1024 × 768 pixels display resolution, but the official definition is broader than that. The initial version of XGA expanded upon IBMs older VGA by adding support for four new screen modes, including one new resolution: 640 × 480 pixels in direct 16 bits-per-pixel (65,536 color) RGB hi-color and 8 bit/px (256 color) palette-indexed mode. 1024 × 768 pixels with a 16- or 256-color (4 or 8 bit/px) palette, using a low frequency interlaced refresh rate. XGA-2 added a 24-bit DAC, but this was used only to extend the available master palette in 256-color mode, e.g. to allow true 256-greyscale output. Other improvements included the provision of the previously missing 800 × 600 resolution in up to 65,536 colors, faster screen refresh rates in all modes (including non-interlace, flicker-free output for 1024 × 768), and improved accelerator performance and versatility. All standard XGA modes have a 4:3 aspect ratio with square pixels, although this does not hold for certain standard VGA and third-party extended modes (640 × 400, 1280 × 1024).implement.