Apple Lisa - The Memory Management Unit

Confidential
Lisa Hardware Reference Manual
THE MEMORY MANAGEMENT UNIT
The Memory Management Unit (MHO) helps the Operating System relocate
objects in memory. It also provides memory access controls to
prevent a process from accessing memory which is not aSSigned to it.
The mechanism used is segmentation.
The 68000 outputs 24 bits of address information. The seven most
significant bits (A23 - A17) select one of the 128 segments. The
remaining 17 bits are the offset into the segment. Each segment has
two
associated registers which describe the origin (SORG) and size
(SLIM) of the segment. In addition, each segment is divided into 512
byte pages. The most significant 8 bits of the segment offset
determine the segment page number J and the remaining 9 bits are the
page offset.
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