Major Components - IBM RT Series Hardware Reference Manual

Major Components
CRT Controller
The CRT (Cathode Ray Tube) Controller (CRTC) generates
horizontal and vertical synchronous timings, addressing for the
regenerative buffer, cursor and underline timings, and refresh
addressing for the dynamic RAMs.
Sequencer
The Sequencer generates basic memory timings for the dynamic
RAMs and the character clock for controlling regenerative
memory fetches. It allows the processor to access memory during
active display intervals by inserting dedicated processor memory
cycles periodically between the display memory cycles. Map
mask registers are available to protect entire memory maps from
being changed.
Graphics Controller
The Graphics Controller directs the data from the memory to the
attribute controller and the processor. In graphics modes,
memory data is sent in serialized form to the attribute chip. In
alpha modes the memory data is sent in parallel form, bypassing
the graphics controller. The graphics controller formats the data
for compatible modes and provides color comparators for use in
color painting modes. Other hardware facilities allow the
processor to write 32 bits in a single memory cycle, (8 bits per
plane) for quick color presetting of the display areas, and
additional logic allows the processor to write data to the display
on non-byte boundaries.
Attribute Controller
The Attribute Controller provides a color palette of 16 colors,
each of which may be specified separately. Six color outputs are
IBM Enhanced Graphics Adapter 3