Memory Management System

The Memory Management System includes a paging system, a permit protection system and a ring protection system.

Memory is measured in bytes. 1 Kbytes is 1024 bytes. However, addressing of memory is in words where 1 word is 2 bytes.

In SINTRAN III the memory management system is used for the following purposes:

1. Dynamic memory allocation and paging. The page size is 2 Kbytes (= 2048 bytes).
2. Extension of maximum physical address space from 128 Kbytes to 32 Mbytes (extended modus for NORD-100).
3. Extension of maximum program size (virtual address area) to 128K words independent of the physical memory size.
4. Memory protection between parts of a program, detection attempts to modify read-only areas or executing data.

The smallest part to be given permit protection and ring protection is a segment. The protection bits of a segment are set by the RT loader when the segment is built.