Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!fernwood!decwrl!decvax!ima!esegue!johnl
From: johnl@esegue.segue.boston.ma.us (John R. Levine)
Newsgroups: comp.sys.ibm.pc
Subject: Re: virtual 8086 in the 386
Keywords: ibm, 80386, intel, virtual, multi, multitasking
Message-ID: <1989Sep18.203833.3301@esegue.segue.boston.ma.us>
Date: 18 Sep 89 20:38:33 GMT
References: <[25138e13:1703]comp.sys.ibm.pc@vpnet.UUCP>
Reply-To: johnl@esegue.segue.boston.ma.us (John R. Levine)
Organization: Segue Software, Cambridge MA
Lines: 25

In article <[25138e13:1703]comp.sys.ibm.pc@vpnet.UUCP> akcs.khenry@vpnet.UUCP (Ken Henry) writes:
>I would like to know the maximum number of virtual 8086's can be operated
>on a 80386.  My first guess was 4 but I was told otherwise, so I'm checking
>to see what you guys think.

The actual answer is "one at a time" but it's entirely a function of your
operating system which is in charge of time-sharing among the various
processes on your machine.  I have run five vp/ix DOS sessions at once on my
386 under Unix and could get 8 easily at which point I run out of Unix
virtual screens.  Unix runs vp/ix in virtual memory, so the total size of
your DOS sessions can exceed the actual amount of memory in your machine.
Desqview and Windows/386 also allow many 8086 sessions, but don't provide
virtual memory, and so are limited by the amount of memory you have.  (At
least they didn't the last time I looked which was a while ago.)

In practice, running a whole lot of DOS sessions at once is of limited
utility.  DOS being a single-user system is totally compute-bound, and with
a lot of DOS sessions your machine becomes very sluggish.  What is quite
useful is to have DOS processes in separate windows but with the inactive
windows frozen, which lets you switch from program to program without losing
what you are doing in one when you use another.
-- 
John R. Levine, Segue Software, POB 349, Cambridge MA 02238, +1 617 492 3869
johnl@esegue.segue.boston.ma.us, {ima|lotus}!esegue!johnl, Levine@YALE.edu
Massachusetts has 64 licensed drivers who are over 100 years old.  -The Globe