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From: johnston@oscar.ccm.udel.edu
Newsgroups: comp.sys.mac.hardware
Subject: Re: 16Mhz Mac Classic?
Message-ID: <38717@nigel.ee.udel.edu>
Date: 11 Dec 90 02:07:04 GMT
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Organization: Univ. of Delaware, CCM
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In article <1990Dec10.192355.7500@umiami.ir.miami.edu>, gross@umiami.ir.miami.edu (Mondo) writes...
>In article <1990Dec10.031031.24801@ux1.cso.uiuc.edu>, walk@mrcnext.cso.uiuc.edu (Todd Walk) writes:
>> 
>> My suggestion, for use on the Mac Classic at least (since this is supposed to 
>> be the affordable Mac...), make a 25 pin centronics parrallel port.

>Yeah, it seems silly that while Apple wants to join the rest of the
>world with all their ways of interconnection that they refuse to add
>something as basic as a RS-232C interface.
> 
>I can see what Apple's reasoning would be:
> 
>  in public: "RS-232C would not deliver the type of performance our
>              users expect from the Mac."
> 
>  in private: "By using proprietary techonology, you either buy our
>               stuff or suffer." 
>And I mean that while they helped establish SCSI as a stnadard, they shouldn't
>ignore others so entrenched as RS-232C.

Sorry ... the 25-pin centronics interface may be common, but RS-232C it ain't.
RS-232C is a serial transmission protocol.  Many computing devices such as
IBM PC XT's used a DB-25 plug for RS-232 cables, but the protocol defines the
functions of the wires rather than a particular plug or cable arrangement.
Apple uses the RS-232 compatible RS-422 protocol for it's serial communications;
the mini-8 plug and pin definitions may be unusual, but not 'proprietary'.

Even IBM switched from the DB-25 to a DB-9 plug when it introduced the AT;
RS-232 cable confusion was not invented by Apple! 

The Centronics interface is/was a DEC invention, used for parallel rather   
than serial data transmission.  Parallel == one wire per data bit.

This is the protocol that is being phased out, for the most part.  
Even PC-compatible printers are increasingly going with the serial
protocol because it is simpler to implement for LAN-shared printers.

I bet the customer would REALLY squawk if forced to buy parallel
interface laser printers which SOME companies like to sell ...
makes for plenty of business for the switch-box companies, that's
for sure.

Bill (johnston@oscar.ccm.udel.edu)
Bill Johnston; 38 Chambers St.; Newark, DE 19711; (302)368-1949