COE 628 Lecture Notes - Lecture 8: Memory Management Unit, Logical Address, Limit Up
30 Mar 2017
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Document Summary
Cpu logical address mmu physical address memory. Simple mmu every time there is a process switch, and there is a context switch, mmu needs to be reprogrammed for the running task. The physical address = logical address + base. Logic address (translate) added to relocation address. If there is an error, then there is an interrupt. An address is followed my segment number and an offset. Descriptor consists of base, limit, permissions, present, write, user mode operation. Every single descriptor has its own base limit. Up to 64k descriptors, roughly 4 bytes long, less than 300 kb to hold the entire table. Easy to share between different process, useful for dynamically linked libraries (ie. printf) Recall 2 modes of operation (kernel vs user) Segments can be huge, this is a problem because the format of the code. Initialization of variables is long, but the calculations are short as they occur in a loop.
