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15SB-6862
System Memory Map
Timers
The system has three programmable timers/counters
controlled by timer/counter chips and defined as channels 0
through 2 as follows:
Channel 0: System Timer
Channel 1: Refresh Request Generator
Channel 3: Tone Generation for Speaker
Address (hex) Name Function
000000 to
9FFFFF
640 KB motherboard system memory
0A0000 to
0BFFFF
128 KB video display
ROM
reserved for graphics
0C0000 to
0DFFFF
128 KB I/O
expansion ROM
reserved for ROM on
I/O
0E0000 to
0EFFFF
64 KB reserved on
motherboard
duplicate code
assignment at FE0000
0F0000 to
0FFFFF
64 KB ROM on
motherbord
duplicate code
assignment at FF0000
100000 to
FDFFFF
maximum memory is
15 MB
I/O channel memory
FE0000 to
FEFFFF
64 KB reserved on
motherboard
duplicate code
assignment at 0E0000
FF0000 to
FFFFFF
64 KB reserved on
motherboard
duplicate code
assignment at 0F0000