Professional Graphics Controller
The PGC's matching display was the IBM 5175, an analog RGB monitor that is unique to it and not compatible with any other video card without modification. With hardware modification, the 5175 can be used with VGA, Macintosh, and various other analog RGB video sources. Some surplus 5175s in VGA-converted form were still sold by catalog retailers such as COMB as late as the early 1990s.
Introduced in 1984, the Professional Graphics Controller (often called "Professional Graphics Adapter" and sometimes "Professional Graphics Array") offered higher resolution and color depth than EGA, and supported 256 colors at higher resolutions than VGA, supporting resolutions up to 640×480 with 256 colors and a refresh rate of 60 Hertz. This mode is not BIOS-supported. It was intended for the computer-aided design market and included 320 kB of display RAM and an on-board Intel 8088 microprocessor. The 8088 was placed directly on the card to permit rapid updates of video memory. Other cards forced the PC's CPU to write to video memory through a slower ISA bus. While never widespread in consumer-class personal computers, its US $4,290 list price compared favorably to US$50,000 dedicated CAD workstations of the time. It was discontinued in 1987 with the arrival of VGA.
The display adapter was composed of three physical circuit boards (one with the on-board microprocessor, firmware ROMs and video output connector, one providing CGA emulation, and the third mostly carrying RAM) and occupied two adjacent expansion slots on the XT or AT motherboard; the third card was located in between the two slots. The PGC could not be used in the original IBM PC without modification due to the different spacing of its slots.
In addition to its native 640 x 480 mode, the PGC optionally supported the documented text and graphics modes of the Color Graphics Adapter, which could be enabled using an onboard jumper. However, it was only partly register-compatible with CGA.
- IBM. 5175 Professional Graphics Display and Controller Announcement Letter. 1984-09-10 ().
- Professional Graphics Adapter pictures