IBM RT Series Hardware Reference Manual page 142

Located on the adapter is a feature connector that provides access
to internal functions through a 32-pin berg connector. A separate
64-pin connector provides an interface for graphics memory
expansion.
The following is a block diagram of the Enhanced Graphics
Adapter:
CPU
Addr.
CPU
Data
~
J
'"
rl
v
~~
4
..
r
CRTC
.. ..
LSI
4~
. .
...
. .
r
0--
~
..
...
r---
SEQ
LSI
I--
MUX
~
....
GRAPH
.:
LSI
'"
...
GRAPH
...
LSI
... ...
' - -
~,
,
n,
..
. .
.... ATTRIB
... LSI
. .
r
Enhanced Graphics Adapter Block Diagram
2 IBM Enhanced Graphics Adapter
H
1~
. .
..
r
BIT 0
~
I--
MAP ~
.
. .
3~.
~
r
. .
BIT 2
-4
-
MAP
~.
01 RECT
DRIVE
OUTPUT