Professional Graphics Controller
| Company type | Product |
|---|---|
| Industry | Computer hardware |
| Founded | 1984 |
| Founder | IBM |
| Defunct | 1987 |
| Products | Graphics card |
Professional Graphics Controller (PGC, also referred to as Professional Graphics Adapter or Professional Graphics Array) is a graphics card created by IBM in 1984 specifically for personal computers. It consists of three linked PCBs, an integrated processor, and dedicated memory, making it the most sophisticated graphics solution available for the IBM XT at its debut. The card was designed primarily for professional uses such as CAD.
The PGC delivered a maximum resolution of 640×480 pixels with support for 256 colors displayed on an analog RGB monitor running at 60 Hz—outperforming the earlier CGA and EGA standards. This high-resolution mode operated without BIOS assistance. Featuring 320 KB of video RAM and an onboard Intel 8088 microprocessor executing graphics routines stored in a 64 KB ROM, it reduced the processing load on the host CPU, thereby enhancing overall system performance.
At launch, the PGC was priced around , with an additional $1,295 required for the accompanying display. This represented a more affordable alternative to specialized CAD workstations, which typically cost about $50,000, even when combined with the $4,995 price tag of an IBM PC XT Model 87. The product line was phased out by 1987 after newer standards like VGA and 8514 were introduced.
Software support
Aimed at CAD professionals, the PGC had relatively limited software compatibility. Supported applications included IBM’s Graphical Kernel System, P-CAD 4.5, Canyon State Systems’ CompuShow, and AutoCAD 2.5.
Output capabilities
The PGC offers:
- Template:Resx resolution with 256 colors selected from a 4,096-color (12-bit RGB) palette.
- Color Graphics Adapter text and graphics modes, utilizing an 8×16 pixel font and providing 400 pixel rows.
It supports six distinct color palette configurations:
- Standard 256-color palette – low nibble controls intensity, high nibble defines color;
- 16-color palette – operates as two separate 16-color planes with conditional bit utilization;
- 2-3-3 palette (Palette 2) – bit allocation divided among red, green, and blue channels;
- 3-2-3 palette (Palette 3) – alternative RGB bit distribution scheme;
- 3-3-2 palette (Palette 4) – another variant of RGB bit assignment;
- 6x6x6 color cube – featuring six gradations each for red, green, and blue.
Operation
The adapter consists of three circuit boards: one housing the onboard CPU, firmware ROMs, and video output circuitry; another dedicated to CGA emulation; and a third mainly populated with RAM modules. Installation requires two adjacent expansion slots on XT or AT motherboards or within the Expansion Unit, with the third board positioned between them. The PGC cannot be used in the original IBM PC without the 5161 Expansion Unit because of slot spacing constraints.
In addition to its proprietary high-resolution mode, the PGC optionally supports documented CGA text and graphics modes through an onboard jumper setting; however, its CGA register compatibility is only partial.
Related monitor
The PGC’s companion display was the IBM 5175, an analog RGB monitor designed exclusively for this card and incompatible with other video adapters without modification. With hardware alterations, the 5175 could be adapted to accept signals from VGA, Macintosh, and other analog RGB sources. Some surplus units modified for VGA compatibility were sold by catalog retailers such as COMB into the early 1990s.
Hardware clones
- Matrox PG-640, PG-1280, and QG-640 models designed for DEC MicroVAX
- Dell NEC MVA-1024 graphics card
- Everex EPGA series
- Orchid Technology TurboPGA line
- Vermont Microsystems IM-640 and IM-1024 units
See also
References
- Notes
- Mueller, Scott (1992) Upgrading and Repairing PCs, Second Edition, Que Books, - references 3 slots and "adapter"
- A Professional Graphics Controller authored by K. A. Duke and W. A. Wall, IBM Systems Journal