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From: jpdres10@usl-pc.UUCP (Green Eric Lee)
Newsgroups: comp.arch,comp.unix.wizards,comp.os.misc
Subject: Re: Shared libraries (Was: Re: Big Programs Hurt Performance)
Message-ID: <83@usl-pc.UUCP>
Date: Tue, 13-Oct-87 12:06:10 EDT
Article-I.D.: usl-pc.83
Posted: Tue Oct 13 12:06:10 1987
Date-Received: Fri, 16-Oct-87 02:41:31 EDT
References: <8714@utzoo.UUCP> <286@usl> <73@usl-pc.UUCP>
Reply-To: elg@usl.UUCP
Organization: Univ. of Southwestern La., Lafayette
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In message <73@usl-pc.UUCP>, mahler@usl-pc.UUCP (Stephen J. Mahler) says:
>> Needless to say, the Amiga OS is not Unix, for one thing, Unix isn't
>> going to run on a 512K machine with no MMU and two floppies...
>DEC machines of PDP design included versions that did not include
>MMUs.  The two that jump to mind are the pdp-11/20-15-10 and the
>LSI-11/03 series.  UNIX ran on these machines.  The straight forward
>approach was called MINI-UNIX.  It had features between V6 and V7
>and the only real stripping of the OS was the removal of account "groups"
>(/etc/group, newgrp, chgrp, etc.).  It did run on systems that had only
>two floppies (like the AED 8 inch floppy system with about 1 meg per
>drive).  It ran well, even from the portable generator on the
>corn combine !!   .........  Steve

I suspect that this "MINI-UNIX" was the version that swapped the
entire used address space whenever there was a context switch. I
seriously doubt whether it was as powerful as the current crop of
68000/no MMU OS's such as OS-9 and TRIPOS (AmigaDOS), which give up
the "fork" call in favor of a "spawn" call in order to put more than
one process in a single address space (with fork, you'd have to
re-adjust every pointer on the heap when you duplicated it for the new
process, or else keep tags hanging around telling you the data type --
anathema for "C").

In any event, this whole ball of hair started with "Well, why doesn't"
<insert machine name here> "run Unix instead of some odd-ball
operating system that I've never heard of?" The answer, once again, is
because <insert machine name> was designed to cost around $1,000, and
thus left out hardware (MMU & hefty hard drive) necessary to run a
MODERN Unix (Sys V.2 or BSD -- forget all these v6's and such, nobody
would WANT to use something like that nowadays, although I'm sure it
was revolutionary enough originally).

--
Eric Green  elg@usl.CSNET       from BEYOND nowhere:
{ihnp4,cbosgd}!killer!elg,      P.O. Box 92191, Lafayette, LA 70509
{ut-sally,killer}!usl!elg     "there's someone in my head, but it's not me..."