Extended Graphics Array (XGA)

Release date	1990; 35 years ago (1990)
History
Predecessor	8514/A
Successor	XGA-2

TheeXtended Graphics Array (usually calledXGA) is agraphics card manufactured byIBM and introduced for theIBM PS/2 line of personal computers in 1990 as a successor to the8514/A. It supports, among other modes, adisplay resolution of1024 × 768pixels with256 colors at 43.5 Hz (interlaced), or640 × 480 at 60 Hz (non-interlaced) with up to 65,536 colors.^[2][3] The XGA-2 added an800 × 600 65,536 color mode and1024 × 768 60 Hz non-interlaced.^[2]

The XGA was introduced at $1095 with 512KVRAM and additional $350 for the 512 KB memory expansion (equivalent to $2600 and $840, respectively, in 2024).^[4][2] As with the 8514/A, XGA required aMicro Channel architecture bus at a time whenISA systems were standard, however due to more extensive documentation and licensing ISA clones of XGA were made. XGA was integrated into the motherboard of the PS/2 Model 95 XP 486.^[3]

An improved version called XGA-2 was introduced in 1992 at $360, worth $810 in 2024 dollars.

XGA gives its name to the resolution1024 × 768, as IBM'sVGA gave its name to640 × 480, despite the IBM 8514/A andPGC cards respectively supporting those resolutions prior to the eponyms.

The 8514 had used a standardisedAPI called the "Adapter Interface" or AI. This interface is also used byXGA,IBM Image Adapter/A, and clones of the 8514/A and XGA such as theATI TechnologiesMach 32 andIITAGX. The interface allows computer software to offload common2D-drawing operations (line-draw,color-fill, and block copies via ablitter) onto the hardware. This frees the hostCPU for other tasks, and greatly improves the speed of redrawing a graphics visual (such as apie-chart orCAD-illustration).^[2][3] Hardware-level documentation of the XGA was also made, which had not been available for the 8514/A.^[3]

XGA introduced a 64x64 hardwaresprite which was typically used for themouse pointer.

• Register-compatible with VGA^[3]
• Adds a 132 column text mode and high color in640 × 480^[3]
• Requires a minimum of80386 host CPU^[3]
• Provides a 3-dimensional drawing space called a "bitmap" which may reside anywhere in system memory^[3]
• Adds a sprite for a hardware cursor^[3]
• The Adapter Interface driver is moved to a.SYS file instead ofTSR program^[3]
• Provisions made formultitasking environment^[3]
• XGA can act asbus master and access system memory directly^[3]
• Hardware level documentation has been provided by IBM^[3]

XGA-2 added support for non-interlaced1024 × 768 and made 1MB VRAM standard. It had a programmablePLL circuit and pixel clocks up to 90 MHz, enabling a 75 Hz refresh rate at1024 × 768. The800 × 600 resolution was added with 16 bit high color support. TheDAC was increased to 8 bits per channel, and the accelerated functions were enabled at 16 bit color depth. Faster VRAM also improved performance.^[2]

The XGA offered:

• 640 × 480:
  • graphics mode with 256 colors at once (8-bit) out of 262,144 (18-bit RGB palette);
  • graphics with 65,536 colors at once (16-bit "high color");
  • text mode with 80×34 characters
• 1024 × 768:
  • graphics with 256 colors out of 262,144;
  • text with 85×38 or 146×51 characters

XGA-2 introduced:

• 640 × 480 graphics with 256 colors out of16.7M (24-bit palette);
• 800 × 600 graphics with 65,536 colors at once;
• 1024 × 768 graphics with 256 colors out of16.7M

Later clone boards offered additional resolutions:

• 640 × 480 graphics with16.7M accessible colors at once (if it were possible with640 × 480 pixels)(24-bit "true color");
• 800 × 600 graphics with16.7M colors at once;
• 1280 × 1024 graphics with 65,536 and 16.7M colors at once

Wikimedia Commons has media related toXGA.

Unlike with the 8514/A, IBM fully documented the hardware interface to XGA. Further, IBM licensed the XGA design toSGS-Thomson (inmos) andIntel. The IIT AGX014 was largely compatible with the XGA-2 and offered some enhancements.

TheVESA Group introduced a common standardized way to access features like hardware cursors, Bit Block transfers (Bit Blt), off screensprites, hardware panning, drawing and other functions withVBE/accelerator functions (VBE/AF) in August 1996. This, along with standardiseddevice drivers for operating systems such asMicrosoft Windows, eliminated the need for a hardware standard for graphics.

• List of IBM products
• List of defunct graphics chips and card companies

• Jake Richter (1992).Power Programming the IBM XGA. MIS Press.ISBN 9781558281271.
• Richard F. Ferraro (1994).Programmer's Guide to the EGA, VGA, and Super VGA Cards. Addison-Wesley.ISBN 9780201624908.

• Computer display standards
• IBM video hardware
• Graphics cards
• Computer-related introductions in 1990
• Computer-related introductions in 1992
• IBM PS/2

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