Description - IBM RT Series Hardware Reference Manual

Description
The IBM Enhanced Graphics Adapter (EGA) is a graphics
controller that supports both color and monochrome direct drive
displays in a variety of modes. In addition to the direct drive port,
a light pen interface is provided. Advanced features on the
adapter include bit-mapped graphics in four planes and a RAM
(Random Access Memory) loadable character generator. Design
features in the hardware substantially reduce the software
overhead for many graphics functions.
The Enhanced Graphics Adapter provides Basic Input Output
System (BIOS) support for both alphanumeric (A/N) modes and
all-points-addressable (AP A) graphics modes, including all modes
supported by the Monochrome Display Adapter and the
Color/Graphics Monitor Adapter. Other modes provide APA
640x350 pel graphics support for the IBM Monochrome Display,
full 16 color support in both 320x200 pel and 640x200 pel
resolutions for the IBM Color Display, and both A/N and APA
support with resolution of 640x350 for the IBM Enhanced Color
Display. In alphanumeric modes, characters are formed from one
of two ROM (Read Only Memory) character generators on the
adapter. One character generator defines 7x9 characters in a
9x14 character box. For Enhanced Color Display support, the
9x 14 character set is modified to provide an 8x 14 character set.
The second character generator defines 7x7 characters in an 8x8
character box. These generators contain dot patterns for 256
different characters. The character sets are identical to those
provided by the IBM Monochrome Display Adapter and the IBM
Color / Graphics Monitor Adapter.
The adapter contains 64K bytes of storage configured as four
16K byte bit planes. Memory expansion options are available to
expand the adapter memory to 128K bytes or 256K bytes.
The adapter is packaged on a single 13-1/8 inch (333.50 mm)
card. The direct drive port is a right-angle mounted connector at
the rear of the adapter and extends through the rear panel of the
system unit. Also on the card are five large scale integration
(LSI) modules custom designed for this controller.
IBM Enhanced Graphics Adapter 1