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From: kevin@harvard.ARPA (Kevin Crowston)
Newsgroups: net.micro.mac
Subject: Connecting two MACs for MazeWars
Message-ID: <147@harvard.ARPA>
Date: Wed, 29-May-85 11:50:36 EDT
Article-I.D.: harvard.147
Posted: Wed May 29 11:50:36 1985
Date-Received: Fri, 31-May-85 02:39:22 EDT
References: <517@x.UUCP> <206@nlm-vax.ARPA>
Distribution: net
Organization: Aiken Computation Laboratory, Harvard
Lines: 43

A recent article suggested the following to connect two macintoshes:

> You can connect two Macs to play without AppleTalk.  The cable which
> comes with the development system is sufficient, a functional equivalent
> may be made by connecting two ImageWriter cables back-to-back: pin 7
> straight across and pins 2 and 3 swapped.

However, a later article gave the following as a pinout for the serial
port (which I assume is the same as the line printer port):
 
> The serial port is RS422, NOT RS-232 !  If you wire it right,
> most RS-232 devices won't care.
> 
> Pinout:
> 
> 1	Ground
> 2	+5
> 3	Ground
> 4	Transmit Data +
> 5	Transmit Data -
> 6	+12
> 7	Incoming handshake
> 8	Receive Data +
> 9	Receive Data -

The second author adds that he converts from RS422 to RS232 as
follows:

> MAC Pin	UNIX Pin
> 1		7
> 5		2
> 9		3

Is it, as I suspect, that the first set of pinouts is actually for
RS232 and not for the 9-pin plug that's on the back of the MAC?  That
is, shouldn't I really be connecting mac pin 1 to 1, 5 to 9 and 9 to 5?

Kevin Crowston
MIT Sloan School
-- 
INC
Kevin Crowston			UUCP: ...!wjh12!harvard!kevin
Aiken Computation Lab		ARPA: kevin@harvard.ARPA