Path: utzoo!mnetor!uunet!nuchat!sugar!peter
From: peter@sugar.UUCP (Peter da Silva)
Newsgroups: comp.arch
Subject: Re: Horizontal pipelining [really: multi-tasking is alive and well]
Message-ID: <1314@sugar.UUCP>
Date: 26 Dec 87 17:25:27 GMT
References: <201@PT.CS.CMU.EDU> <388@sdcjove.CAM.UNISYS.COM> <988@edge.UUCP> <1062@winchester.UUCP>
Organization: Sugar Land UNIX - Houston, TX
Lines: 45
Summary: Multitasking does *not* require a lot of resources.

In article <1062@winchester.UUCP>, mash@mips.UUCP (John Mashey) writes:
> Given that PCs were hardly the first single-user computers,
> and that multi-tasking on single-user systems has existed almost as long as
> the systems have, I'd guess that the current prevalence of
> single-tasking systems is just an anomoly of the cost/performance &
> feature (i.e. lack of builtin memory-mapping) combinations of late 70s /
> early 80s microprocessors.

I'd say that the reason was that IBM dived into the market with a machine that
was at most a slight improvement over existing single-tasking systems just as
multitasking CP/M derivitives (MP/M, CP/M 3.x) and reasonable micro-based
UNIX boxes (Onyx, etc...) were just getting into the water. IBM's entry swamped
them and they never came up again. The industry is just now beginning to
recover from the advent of the IBM-PC.

> For many years, each successive generation of
> computers (mainframes, minis, micros) seemed to repeat most of the mistakes
> of the earlier ones.  Now that current micros have:
> 	a) useful addressability (32-bits)

Multitasking doesn't require a large adress space. UNIX *used to* run fine in
256K with a user or two.

> 	b) on-chip MMUs (hence no cost-cutting reason to omit them)

Multitasking doesn't require an MMU. VenturCom has been selling UNIX for the 
IBM-PC for years. Or look at the Coco...

> 	c) reasonable design for use with high-level languages

6809, anyone? Back to the Coco.

> 	d) more-or-less reasonable design for use with multi-tasking OSs

Please explain what you mean by this.

> and given that DRAMs are getting big enough that it's almost HARD to build
> tiny-memory systems, the original reasons for this aberration are rapidly
> going away, leaving only the software legacy [unfortunately].

The original reason for this abberation is still around, but it's working hard
to catch up.
-- 
-- Peter da Silva  `-_-'  ...!hoptoad!academ!uhnix1!sugar!peter
-- Disclaimer: These U aren't mere opinions... these are *values*.