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From: dave@sdeggo.UUCP (David L. Smith)
Newsgroups: comp.arch,comp.unix.wizards
Subject: Re: Free Software Foundation (was: Re: Mach, the new standard?)
Message-ID: <105@sdeggo.UUCP>
Date: Mon, 28-Sep-87 23:31:10 EDT
Article-I.D.: sdeggo.105
Posted: Mon Sep 28 23:31:10 1987
Date-Received: Wed, 30-Sep-87 06:16:01 EDT
References: <8490@think.UUCP> <1745@ncr-sd.SanDiego.NCR.COM> <819@sugar.UUCP> <6488@brl-smoke.ARPA>
Organization: Lazy Programmer's Society of San Diego
Lines: 26
Xref: mnetor comp.arch:2413 comp.unix.wizards:4569

In article <6488@brl-smoke.ARPA>, gwyn@brl-smoke.ARPA (Doug Gwyn ) writes:
> In article <819@sugar.UUCP> peter@sugar.UUCP (Peter da Silva) writes:
> >You can run way more users on and get way better real-time response
> >from a PDP 11/70 than any VAX you care to name.
> 
> Both 22-bit PDP-11s and VAXes have to perform two levels of address
> translation.  Some VAXes provide poorer peripheral I/O paths, but
> apart from that there is little difference in their real-time abilities.

There may be little difference in their actual processor speeds, but as
far as actual response, it's pretty incredible.  We used to run 30 users
on a PDP-11/70 with 512K (bytes!) of memory and an RM03.  No shared libraries,
no shared executables, each user had their own task.  However, since the
swap size is so small (64 or 128K) you can swap them in and out without
hardly even noticing it.  It would have really flown with a full 4M.
Heck, I used to run real-time terminal programs written in interpreted
BASIC-Plus and have them work (but, there couldn't be much of anything else
on the system).



-- 
David L. Smith
{sdcsvax!amos,ihnp4!jack!man, hp-sdd!crash, pyramid}!sdeggo!dave
sdeggo!dave@amos.ucsd.edu 
"How can you tell when our network president is lying?  His lips move."