Path: utzoo!attcan!uunet!mcvax!diku!dkuug!dde!tpo
From: tpo@dde.uucp (Thomas P.S. Olesen)
Newsgroups: comp.arch
Subject: Re: Is Shared Memory Necessary?
Message-ID: <448@Aragorn.dde.uucp>
Date: 30 May 88 21:47:57 GMT
References: <685@thalia.rice.edu> <43700039@uicsrd.csrd.uiuc.edu>
Reply-To: tpo@dde.uucp (Thomas Peter Sonne Olesen)
Organization: Dansk Data Elektronik A/S, Herlev, Denmark
Lines: 35

In article <43700039@uicsrd.csrd.uiuc.edu> turner@uicsrd.csrd.uiuc.edu writes:
>
>Why is it that everyone seems to assume that machines must either have
>shared memory OR distributed memory, never a little of both?  From my
>point of view I would like to see a machine with: fast local memory;
>slower, but deeply pipelined, shared memory; and a thin global sync
>bus (for barrier sync).  We have had memory heirarchies for decades
>now, why should they cease to be useful now?

The Supermax computer made by "my" company, has both distributed and
shared memory. 
The Supermax is a multiprocessor machine with up to 8 x 68020 
application processors, and up to 8 other 680x0/8085 processores for
handling IO.

Every processor has local memory (up to 256Mb), but they are made
so they can setup the mmu and make data read/write/read-modify-write
in all other cpues memory, using the common bus. But NOT instruction 
fetch.

This achitecture makes it possible to run all processors at high
speed and have fast memory access AND have shared memory.

The OS is SVR3.1 and shard memory for users processes is fully
supported. A memory access to another cpu is a little slower
than a local access. I think remote access take about 4 times a
local access.

Thomas P. Olesen

-- 
*****************************************************************************
Thomas P.S. Olesen                               Dansk Data Elektronik A/S
E-mail: ..!mcvax!diku!dde!tpo                    System Software Department
        or       tpo@dde.dk