Professional Graphics Controller

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PGC card

The Professional Graphics Controller ( PGC ) was a graphics card manufactured by IBM for the PC XT and PC AT . Compared to other contemporary graphics solutions, the PGC was very advanced. It offered hardware acceleration for 2D and 3D graphics for professional CAD applications and consisted of three interconnected circuit boards that housed their own processor and memory.

monitor

The IBM 5175 monitor is the appropriate monitor for the PGC card. It is an analog RGB monitor that is specially designed for this card. Normally it cannot be operated with any other graphics card, but it can be converted and can then be operated with VGA cards, old Macintosh computers and other analog RGB video sources. Remaining stocks of the 5175 converted to VGA were partly sold in the American mail order business in the early 1990s.

market

The PGC was introduced in 1984 and offers a higher resolution and color depth than the EGA standard from the same year. With the support of a resolution of 640 × 480 pixels with 256 colors (from a palette of 4096 colors) and 60 Hz refresh rate, the PGC is even superior to the first VGA cards, which were introduced in 1987. Games with this graphic quality were only implemented for SVGA cards in the early to mid-1990s. However, the mode is not supported by a BIOS interface.

The PGC was aimed at the market for professional CAD workstations and has 320 KB of video memory - which was gigantic at the time - and its own Intel 8088 processor, with which the hardware could support applications in tasks such as rotating images in 2D. The PGC never found widespread use in computers for ordinary users, but an IBM PC XT / AT with a PGC, which had a list price of US $ 4,290 , was a very attractive alternative to CAD workstations for professional users , which often cost around $ 50,000.

With the appearance of VGA cards, the PGC was finally discontinued.

Specialty

In the 1980s, common graphics adapters were developed with a view to the limits of the television sets that were still often used at the time; this is how the CGA resolution of 320 / 640x200 pixels came about. These, however, were rectangular, which was perceived as annoying given the comparatively short distance to computer monitors; Graphics had to be corrected mathematically or were displayed distorted. With PGC, the pixels were not only finer, due to the ratio of 640/480, corresponding to the 4/3 of the monitors, they were also exactly square and were perceived as far less annoying. A display of PGC on TV sets was not planned; the graphics adapters were only affordable for professional users with appropriate monitors.

construction

The PGC consists of three boards. One contains the main graphics processor, firmware ROM chips, and video output; one is responsible for emulating the CGA , and the third mainly contains the graphics memory. The PGC occupies two ISA slots on a mainboard; the third board is located between the other two, which take up the space above the slots. For reasons of space, the PGC could only be used from the PC XT .

In addition to the standard mode of 640 × 480 pixels, the PGC supports the official text and graphic modes of the CGA on request . This can be set with a jumper on the circuit board. However, the PGC is only partially compatible with the CGA at register level, so the CGA emulation can be deactivated and the PGC can then be operated in combination with a real CGA or EGA card without conflict.

literature

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