Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!maverick.ksu.ksu.edu!iowasp.physics.uiowa.edu!ns-mx!pyrite.cs.uiowa.edu
From: jones@pyrite.cs.uiowa.edu (Douglas W. Jones,201H MLH,3193350740,3193382879)
Newsgroups: comp.arch
Subject: Re: Microcomputer Bus Multiprocessing
Message-ID: <5015@ns-mx.uiowa.edu>
Date: 22 Mar 91 21:12:02 GMT
References: <1991Mar22.185924.10593@sj.nec.com>
Sender: news@ns-mx.uiowa.edu
Lines: 26

It appears that there are many people who don't realize that snooping
caches on bus based multiprocessors are a reality in the marketplace.

Encore and Sequent have both been offering products based on this
technology for some time.  The Encore Multimax uses NS 32000 family
microprocessors, while Sequent builds machines around the M 68000 and
Intel 80x86 families.

In addition, the DEC Firefly is built around microvax processors, but
I don't know if they built it commercially or just for in-house research.

We have 2 Encore Multimax machines at Iowa, both with around 18
processors.  One is used as a workhorse supporting undergraduate
computer science instruction, the other supports only research users.
Parallel processing on the Multimax is supported at the lowest level
with shared memory and spin-locks.  There is a threads package sitting
on top of this low level.

The Encore operating system (MULTIMAX) is a version of UNIX with memory
sharing between processes allowed on a page by page basis (mark the page
as shared, then fork); theres a suite of library routines to manage a
shared heap using a shared version of malloc -- that's how I usually
do shared memory applications on this machine.

					Doug Jones
					jones@cs.uiowa.edu