Apple Lisa - Memory Configurations

Confidential
Lisa Hardware Reference Manual
MEMORY
All memory is divided into three parts: main system memory (RAM),
I/O memory, and special I/O memory. Main memory can contain up to
two megabytes of RAM. I/O memory is used by all system I/O devices.
Special I/O memory is used to boot the machine and to run the
self-diagnostic tests. The Memory Management Unit transforms
addresses generated by the 68000 into actual memory locations.
MEMORY CONFIGURATIONS
The memory boards contain four rows of RAM chips with 18 chips in
each row. This configuration provides byte parity memory. Since
the chips can be either 16K or 64K RAMs, the board capacity is either
I28K or SIlK bytes. The boards can be jumpered to reduce total
memory capacity by stuffing only one or two rows. A partially
stuffed memory board containing 64K RAMs can yield either 128K or
256K bytes.
The memory boards contain the address recognition circuitry to make
them self configuring. An n byte board automatically occupies the
next n bytes in the main memory address space. Memory capacity can
therefore be increased merely by plugging in another board.
POSSIBLE MEMORY QDNFlGURATIONS
Configuration Board 1
Board
2
Board
1· Board 2
Total
Number Chips
Chips
Size Size Size
7-Jul-81
----
----------
1 16K
I28K I28K
2 16K
16K 128K
128K
256K
2 64K
256K
256K
3
64K 512K S12K
4
16K
64K
128K S12K
640K
4 64K 16K S1lK 128K 640K
S
64K 64K
S1lK 256K
768K
5
64K 64K 256K S12K 768K
6
64K
.
64K
SIlK S12K 1024K
Since only four rows of RAM fit on a board, the maximum memory size is
one megabyte.
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