[comp.sys.acorn] Virtual memory for the Archimedes

vanaards@p4.cs.man.ac.uk (Steven van Aardt) (06/20/91)

  Has a Virtual Memory system been implemented for the Archimedes ?
(Obviously RISCiX has too have one - which begs the question "Why 
 did Acorn not release it as part of the Archimedes package ?")

 Is it possible to read the logical -> physical mappings from the MEMC ?

-- Steve
-- 
  ---------------------------------------------------------------------------
  -       JANET E-mail : vanaards@uk.ac.man.cs.p4 (Steven van Aardt)       -- 
  -- Warning this user has been designated for termination on the 21.6.91  --
  ---------------------------------------------------------------------------

Albert.Koelmans@newcastle.ac.uk (Albert Koelmans) (06/20/91)

vanaards@p4.cs.man.ac.uk (Steven van Aardt) writes:


>  Has a Virtual Memory system been implemented for the Archimedes ?
>(Obviously RISCiX has too have one - which begs the question "Why 
> did Acorn not release it as part of the Archimedes package ?")

The term Virtual Memory tends to be used in two different ways: either as a
synonym for 'swapping' or as a reference to MEMC operation (logical to
physical page translation). If you are referring to the second kind, the
answer is yes -  RiscOs obviously uses it. It's straightforward to implement.
The first kind is very tricky (because of the problem of recovering the
machine state at the time the page fault occurred).

Since RiscIx is a completely different system
from RiscOs it's not immediately obvious that the same code could be used in
both systems :-)


> Is it possible to read the logical -> physical mappings from the MEMC ?

Yep - there's a program called 'memmap' on the info server that does it. The
output is a bit messy, but could easily be fixed.

Albert


JANET:  Albert.Koelmans@uk.ac.newcastle
UUCP:   ...!ukc!newcastle.ac.uk!Albert.Koelmans
Computing Laboratory, University of Newcastle upon Tyne,
Newcastle upon Tyne, NE1 7RU, UK (telephone +44 091-2228155,fax 2228232)