Re: base and bounds, Why I've Dropped In

On 6/15/2025 12:44 PM, John Levine wrote:

According to Stephen Fuld  <sfuld@alumni.cmu.edu.invalid>:

[ base and bounds vs paging
An interesting question is whether it is worthwhile to do both.

 Multics had segments of variable size, with each segment paged.
That worked, give or take the inevitable problem of running out of
address bits.

I didn't know that about Multics.  Thanks John.  ISTM that their approach is the opposite of Unisys's approach.  They put the pages within the base and bounds, whereas Unisys puts the base and bounds "over" the pages.  I think the Mill's approach is to put them "side by side".
I don't want to use the word segments, as that has bad connotations that aren't relevant here.  For historical reasons, Unisys uses the word "bank" to describe the logical addresses between the base and the bound.

I think that is an insoluble problem with base and bounds.  However
you divide up the address space into sections, some sections will
be too small.

I don't think so.  Probably with the Multics approach, but not with the Unisys approach.  You can make the individual "sections"/banks as large as you want.
--
  - Stephen Fuld
(e-mail address disguised to prevent spam)