Subject: Re: Considering port to new processor
To: None <firstname.lastname@example.org>
From: Erik E. Fair <email@example.com>
Date: 03/30/2001 15:34:17
There was a time when UNIX did not page - it swapped. Processes were
either all the way in RAM, or not there at all - no "pages" at all.
On that sort of system, there is no need to support restartable
instructions for page faults.
MMUs do two things:
1. address translation. This makes it possible to use non-PIC
compiled programs, and make non-contiguous sections of memory appear
2. protection. This is what makes UNIX relatively more impervious to
viruses, and prevents a single bogus application program from
crashing the entire system.
The paging stuff is just gravy on top of this.