Extended Graphics Array
| Company type | Product line |
|---|---|
| Industry | Computer hardware |
| Predecessor | 8514/A |
| Founded | 1990 |
| Founder | IBM |
| Headquarters | Armonk, New York , United States |
| Products | Graphics cards (XGA, XGA-2) |
| Parent | IBM |
The eXtended Graphics Array (XGA) is a graphics card created by IBM and introduced in 1990 as part of the IBM PS/2 series, succeeding the 8514/A model. It delivers a screen resolution of pixels displaying 256 colors at 43.5 Hz in interlaced mode, or at 60 Hz non-interlaced with a palette of up to 65,536 colors. The subsequent XGA-2 model enhanced this by supporting at 65,536 colors and a non-interlaced resolution at 60 Hz.
Initially priced at $1095 with 512K VRAM, the XGA offered an optional memory upgrade of an additional 512KB for $350 (adjusted for inflation). Like its predecessor, the 8514/A, it utilized a Micro Channel architecture bus during a period when ISA systems were prevalent; nonetheless, due to extensive documentation and licensing agreements, ISA-compatible XGA clones became available. Furthermore, XGA technology was embedded directly into the motherboard of the PS/2 Model 95 XP 486.
The enhanced XGA-2 model was launched in 1992 with a price tag of $360 (inflation-adjusted).
XGA is distinguished for defining the resolution naming convention, similar to how IBM's VGA established the , despite these resolutions having been supported earlier by IBM's 8514/A and PGC cards.
Features
XGA maintained use of the standardized "Adapter Interface" (AI) API originally developed for the 8514, which was also employed by the IBM Image Adapter/A and compatible clones such as ATI Technologies’ Mach 32 and IIT’s AGX. This interface delegates common 2D drawing tasks—like line rendering, color fills, and block transfers via a blitter—to dedicated hardware. This offloading reduces CPU load and accelerates graphics processing for applications including CAD and data visualization. Unlike the 8514/A, IBM supplied thorough hardware documentation for XGA.
Additionally, XGA introduced a hardware-supported 64x64 pixel sprite, commonly employed as the mouse pointer.
Differences from 8514/A
- Compatible with VGA registers
- Introduces a text mode with 132 columns and supports high-color mode at
- Requires a minimum of an 80386 processor
- Offers a three-dimensional drawing environment called a "bitmap" stored in system memory
- Incorporates a hardware cursor sprite
- Adapter Interface driver transitioned from TSR to a .SYS driver file
- Engineered for multitasking operating systems
- Capable of functioning as a bus master, allowing direct access to system memory
- IBM provided detailed hardware-level documentation
XGA-2
The XGA-2 variant brought non-interlaced support at , standardized VRAM capacity to 1MB, and included a programmable PLL circuit capable of pixel clock frequencies up to 90 MHz. This allowed refresh rates of 75 Hz at . The new resolution was introduced with support for 16-bit high color. The DAC was upgraded to an 8-bit per channel design, while accelerated graphics operations ran at a color depth of 16 bits. Enhanced VRAM speed contributed to improved overall performance.
Output capabilities
The original XGA offered:
- Template:Resx:
- Displaying up to 256 colors (8-bit) selected from an 18-bit RGB palette containing 262,144 colors;
- Supporting up to 65,536 colors (16-bit "high color");
- Text mode featuring an 80×34 character grid
- Template:Resx:
- Displaying up to 256 colors from the same palette;
- Text modes available at either 85×38 or 146×51 characters
With XGA-2, support expanded to include:
- Template:Resx with access to all 16.7 million colors (24-bit palette);
- Template:Resx capable of displaying up to 65,536 colors;
- Template:Resx supporting up to 256 colors from a palette of 16.7 million
Subsequent clone graphics cards further extended capabilities to:
- Template:Resx offering full true color (24-bit) display;
- Template:Resx with full-spectrum color support;
- Template:Resx providing both high-color (65,536) and true color (16.7 million) modes
Clones
IBM provided comprehensive documentation of the XGA hardware interface and authorized SGS-Thomson and Intel to manufacture designs based on it. The IIT AGX014 model maintained significant compatibility with XGA-2 while incorporating several improvements.
In August 1996, the VESA Group established standardized methods for accessing features such as hardware cursors, Bit Blt operations, off-screen sprites, hardware panning, and rendering through VBE/accelerator functions (VBE/AF). Alongside uniform device drivers for operating systems like Microsoft Windows, this development diminished dependency on proprietary graphics hardware standards.