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From: richard@aiai.ed.ac.uk (Richard Tobin)
Newsgroups: comp.arch
Subject: Re: Paging page tables
Message-ID: <2936@skye.ed.ac.uk>
Date: 5 Jul 90 17:46:45 GMT
References: <3300142@m.cs.uiuc.edu> <1990Jun29.154940.22762@tera.com>
Reply-To: richard@aiai.UUCP (Richard Tobin)
Organization: AIAI, University of Edinburgh, Scotland
Lines: 17

In article <1990Jun29.154940.22762@tera.com> bob@colossus.tera.com (Bob Alverson) writes:
>Consider a UNIX process with heap at low addresses going up and stack
>at high addresses going down.  Without a paged page table, all the
>space in between must have page table entries sitting in physical memory.

Or you must have two page tables.

Do operating systems that allow sparse address spaces (eg SunOS 4) use
paged page tables to achieve this?  Is the fact that BSD doesn't use
the Vax's paged page tables the reason why it doesn't support sparse
address spaces?

-- Richard
-- 
Richard Tobin,                       JANET: R.Tobin@uk.ac.ed             
AI Applications Institute,           ARPA:  R.Tobin%uk.ac.ed@nsfnet-relay.ac.uk
Edinburgh University.                UUCP:  ...!ukc!ed.ac.uk!R.Tobin