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 
contiguous.

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.

	Erik <fair@clock.org>