AppleBus info

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From: info-mac@uw-beaver (info-mac)
Newsgroups: fa.info-mac
Subject: AppleBus info
Message-ID:
Date: Sat, 30-Jun-84 14:30:51 EDT
Article-I.D.: uw-beave.1009
Posted: Sat Jun 30 14:30:51 1984
Date-Received: Tue, 3-Jul-84 03:05:06 EDT
Sender: daemon@uw-beave
Organization: U of Washington Computer Science
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From: sequoia!brownell@harvard.ARPA (Dave Brownell)
This is a summary of some information in "Systems and Software", a monthly
trade journal. The article is in the May 1984 issue. I undestand that
the communications protocols were in a state of flux fairly recently, but
I assume the rest is still accurate. If anybody knows more about AppleBus
I'd love to hear it ...

Dave Brownell
Sequoia Systems
Marlborough, MA

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"Buy a computer, get a local area network (almost) free!
Summarized from May '84 "Systems and Software"

Apple realizes that high speed networks such as Ethernet are too pricey
for most PC applications, so it's designed AppleBus. Connections are
to be about $25 each, and will support reliable communications and
resource sharing capabilities. Interfaces to other vendors' networks
will be provided, and to "major standard" networking protocols.

The low connection cost is a result of the "low" 230 kbit/s data rate;
VLSI technology can then be used. (With Ethernet, for example, the
encoding and decoding circuitry must operate too fast for current
VLSI.) Less expensive cabling can also be used.

The long range architecture envisioned has three tiers. The lowest
will be lowspeed nets like AppleBus, used within a small area such as a
department. These will connect to backbones such as 10 Mbit/s Ethernet
or IBM's token passing LAN. [Note -- IBM's ring is still two years away.]
These backbones will handle most connections to the mainframe networks,
the third tier.

To facilitate development of this architecture, AppleBus will be a
completely open system using the ISO reference model. Apple will make
the protocols public and provide interfaces to standard protocols.
Major networking protocol interfaces will include the OSI family,
Xerox's XNS, the DoD's TCP/IP, and IBM's SNA, among others.

AppleBus is a Carrier Sense Multiple Access/Collision Avoidance network
(CSMA/CA). It differs from Ethernet in speed, cost, size, and access
method. It will connect all Apple computers, their peripherals, and
servers. The hardware is mostly built in to MacIntosh and Lisa
computers. Software will be integrated with future OS releases;
updates will be provided free.

AppleBus will handle up to 32 nodes and cover up to 1000 feet using
twisted pair wiring. Control is distributed, so any node may be
removed.

Apple is not worried about the "low" speed since this is certainly
adequate for the environment planned. IBM's PC LAN is about as fast,
and uses a similar access method.

[ There is brief discussion about some of the technical issues such as
the collision avoidance protocol and some protocols. The network layer
provides datagram service, the transport layer provides end to end
reliability services. ]