Extended Graphics Array

(Redirected fromXGA)

TheeXtended Graphics Array(usually calledXGA) is agraphics cardmanufactured byIBMand introduced for theIBM PS/2line of personal computers in 1990 as a successor to the8514/A.It supports, among other modes, adisplay resolutionof1024 × 768pixelswith256 colorsat 43.5Hz(interlaced), or640 × 480at 60 Hz (non-interlaced) with up to 65,536 colors.[2][3]The XGA-2 added an800 × 60065,536 color mode and1024 × 76860 Hz non-interlaced.[2]

Extended Graphics Array (XGA)
The IBM internal XGA logo, designed by Rand Paul[1]
Release date1990;35 years ago(1990)
History
Predecessor8514/A
SuccessorXGA-2

The XGA was introduced at $1095 with 512KVRAMand additional $350 for the 512KB memory expansion (equivalent to $2600 and $840, respectively, in 2024).[4][2]As with the 8514/A, XGA required aMicro Channel architecturebus at a time whenISAsystems 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'sVGAgave its name to640 × 480,despite the IBM 8514/A andPGCcards respectively supporting those resolutions prior to the eponyms.

Features

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The 8514 had used a standardisedAPIcalled 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 32andIITAGX.The interface allows computer software to offload common2D-drawingoperations (line-draw,color-fill,and block copies via ablitter) onto the hardware. This frees the hostCPUfor other tasks, and greatly improves the speed of redrawing a graphics visual (such as apie-chartorCAD-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 hardwarespritewhich was typically used for themouse pointer.

Differences from 8514/A

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  • Register-compatible with VGA[3]
  • Adds a 132 column text mode and high color in640 × 480[3]
  • Requires a minimum of80386host 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.SYSfile instead ofTSRprogram[3]
  • Provisions made formultitaskingenvironment[3]
  • XGA can act asbus masterand access system memory directly[3]
  • Hardware level documentation has been provided by IBM[3]

XGA-2

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IBM micro channel architecture XGA-2 graphics card
Another variant of XGA-2 graphics card

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

Output capabilities

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The XGA offered:

  • 640 × 480:
    • graphics mode with 256 colors at once (8-bit) out of 262,144 (18-bit RGBpalette);
    • 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 × 480graphics with 256 colors out of16.7M (24-bit palette);
  • 800 × 600graphics with 65,536 colors at once;
  • 1024 × 768graphics with 256 colors out of16.7M

Later clone boards offered additional resolutions:

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

Clones

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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.

TheVESAGroup 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 driversfor operating systems such asMicrosoft Windows,eliminated the need for a hardware standard for graphics.

See also

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References

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  1. ^"XGA Logo".Paul Rand Foundation.Retrieved25 September2021.
  2. ^abcdeJon Peddie (8 April 2019)."Famous Graphics Chips: IBM's XGA. The End of an Era".IEEE.org.
  3. ^abcdefghijklmJulio Sanchez; Maria P. Canton (2003).The PC Graphics Handbook.Boca Raton: CRC Press.ISBN9780203010532.
  4. ^1634–1699:McCusker, J. J.(1997).How Much Is That in Real Money? A Historical Price Index for Use as a Deflator of Money Values in the Economy of the United States: Addenda et Corrigenda(PDF).American Antiquarian Society.1700–1799:McCusker, J. J.(1992).How Much Is That in Real Money? A Historical Price Index for Use as a Deflator of Money Values in the Economy of the United States(PDF).American Antiquarian Society.1800–present:Federal Reserve Bank of Minneapolis."Consumer Price Index (estimate) 1800–".Retrieved29 February2024.

Further reading

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  • Jake Richter (1992).Power Programming the IBM XGA.MIS Press.ISBN9781558281271.
  • Richard F. Ferraro (1994).Programmer's Guide to the EGA, VGA, and Super VGA Cards.Addison-Wesley.ISBN9780201624908.