Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!pyramid!csg
From: csg@pyramid.pyramid.com (Carl S. Gutekunst)
Newsgroups: comp.arch
Subject: Re: Single/Multi Tasking position summary (was Re: Single tasking)
Message-ID: <12600@pyramid.pyramid.com>
Date: 4 Jan 88 17:00:34 GMT
References: <60@amelia.nas.nasa.gov> <2428@encore.UUCP>
Reply-To: csg@pyramid.UUCP (Carl S. Gutekunst)
Organization: Pyramid Technology Corp., Mountain View, CA
Lines: 26

In article <2428@encore.UUCP> collins@encore.UUCP (Jeff Collins) writes:
>	General timesharing: A truely parallel machine like the Encore 
>	    Multimax or the (I have to say this for fairness) Sequent Balance.

As long as you are being fair, don't forget the Elxsi 6400, the Pyramid 9800,
and Counterpoint's workstation line. Symmetric parallel processing in general
timesharing is not that uncommon these days.

>	    The multi-CPU VAXen, do not parallelize the most important
>	    aspect of a timesharing machine - I/O.

The difference is that Multi-CPU VAXen (under UNIX, not VMS) are Master/Slave.
The blanket statement that "I/O is not parallelized" is not entirely true,
since the system provides other intelligent I/O interfaces that operate in
parallel with the main CPUs. But it *is* true that the operating system is not
running in parallel, which can be a major bottleneck especially with more than
two CPUs. 

A similar strategy is used by the CCI Power 6/32, the older Celerity systems
(I dunno about the new ones), and the Arete 68010 and 68020 multi-CPU boxes.

Note that any price/performance comparison to DEC is misleading. Any of the
second- or third-tier computer companies can beat DEC on price/performance.
Likewuse with IBM. But this has not stopped either company from selling oodles
of machines, sometimes for good reason, sometimes not.

<csg>