Multi-Color Graphics Array

The Multi-Color Graphics Array or MCGA is a video subsystem built into the motherboard of the IBM PS/2 Model 30, introduced in April 1987, and Model 25, introduced later in August 1987; no standalone MCGA cards were ever made.

The MCGA supports all CGA display modes plus monochrome at a refresh rate of 60  Hz, and with 256 colors (out of an 18-bit RGB palette of 262,144) at 70 Hz. The display adapter uses a DE-15 connector, sometimes referred to as HD-15.

MCGA is similar to VGA in that it had a 256-color mode (the 256-color mode in VGA was sometimes referred to as MCGA) and uses 15-pin analog connectors. The PS/2 chipset's limited abilities prevent EGA compatibility and high-resolution multi-color VGA display modes.

The tenure of MCGA was brief; the PS/2 Model 25 and Model 30 were discontinued by 1992, and the only manufacturer to produce a clone of this display adapter was Epson, in the Equity Ie and PSE-30, since the VGA standard introduced at the same time was considered superior.

Software support

The 256-color mode proved most popular for gaming. 256-color VGA games ran fine on MCGA as long as they stuck to the basic 256-color mode and didn't attempt to use VGA-specific features such as multiple screen pages.

Games lacking support for 256-color graphics were forced to fall back to four-color CGA mode (or not run at all) due to the incompatibility with EGA video modes (, , or , all in 16 colors). Some games, including point-and-click adventures from Sierra On-line and Lucasfilm Games, as well as simulation and strategy titles from Microprose, solved this problem for low-resolution titles by supporting the MCGA's 256-color mode and picking the colors most resembling the EGA 16-color RGB palette, while leaving the other available colors in that mode unused.

Higher resolution titles were often unsupported unless graphics could be converted into either MCGA low or high ( monochrome, which would also support and with some letterboxing) resolution mode in an acceptable fashion. An alternative approach used by a small number of (generally earlier) games was to use four-color CGA assets but make use of the adaptor's ability to freely change the palette for a slightly enhanced appearance.

Output capabilities

MCGA offered:
* monochrome (mode 11h)
* in 256 colors (from a palette of 262,144; mode 13h)

CGA compatible modes:
* text mode with 8×8 pixel font (effective resolution of ; mode 0/1h)
* text mode with 8×8 pixel font (effective resolution of ; mode 2/3h)
* in four colors from a 16 color hardware palette with a pixel aspect ratio of 1:1.2. (mode 4/5h)
* in two colors with a pixel aspect ratio of 1:2.4 (mode 6h)

See also

* List of defunct graphics chips and card companies

References

*

{{IBM personal computers

Computer display standards
IBM PS/2
Multi-Color Graphics Adapter
Computer-related introductions in 1987