Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!shadooby!ginosko!brutus.cs.uiuc.edu!lll-winken!uunet!ncrlnk!ncrcce!pasek
From: pasek@ncrcce.StPaul.NCR.COM (Michael A. Pasek)
Newsgroups: comp.arch
Subject: Re: Shared Memory vs. Distributed Systems
Summary: Sounds like Shared Memory to me....
Keywords: Shared, distributed, message
Message-ID: <1646@ncrcce.StPaul.NCR.COM>
Date: 24 Oct 89 14:16:10 GMT
Expires: 30 Oct 89 05:00:00 GMT
References: <20764@usc.edu>
Reply-To: pasek@c10sd3.StPaul.NCR.COM (M. A. Pasek)
Followup-To: comp.arch
Organization: NCR Comten, Inc.
Lines: 18

In article <20764@usc.edu> vorbrueg@bufo.usc.edu (Jan Vorbrueggen) writes (in
response to article <36597@lll-winken.LLNL.GOV> brooks@maddog.llnl.gov (Eugene Brooks):
>Eugene, ever seen a transputer? Overhead for receiving or sending a 
>message is 19 cycles (630 ns for a 30 MHz part). The actual transfer
>is done by a dedicated DMA machine at a maximum rate of 1.7 Mbyte/s
              ^^^^^^^^^^^^^^^^^^^^^

Although you describe this as "message passing" between the computers,
it sounds to me like you have one "global" memory which is controlled by the
"dedicated DMA machine", and this memory is "shared" by all the "local"
processors.  What difference does it make whether you set some register in
your "dedicated DMA machine" and tell it to move some data to another 
location, or just set an address latch in your micro somewhere and do a
"store" instruction ?  

M. A. Pasek          Switching Software Development         NCR Comten, Inc.
(612) 638-7668              CNG Development               2700 N. Snelling Ave.
pasek@c10sd3.StPaul.NCR.COM                               Roseville, MN  55113