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From: fiddler%concertina@Sun.COM (Steve Hix)
Newsgroups: comp.sys.apple
Subject: Re: Query: Apple Disk drive controller architecture(s)
Message-ID: <31710@sun.uucp>
Date: Thu, 22-Oct-87 17:39:36 EST
Article-I.D.: sun.31710
Posted: Thu Oct 22 17:39:36 1987
Date-Received: Sun, 25-Oct-87 09:46:43 EST
References: <561745777.ralphw@IUS2.CS.CMU.EDU>
Sender: news@sun.uucp
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In article <561745777.ralphw@IUS2.CS.CMU.EDU>, Ralph.Hyre@IUS2.CS.CMU.EDU writes:
> 
> 4) SmartPort (//GS or on disk side of Protocol converter?)
> [Is this another name for the Protocol Converter?]
> It is claimed that if you have a 'smartport' drive (like the UniDisk
> 3.5) you can daisy chain large numbers (7 or 128) of ANY Apple drive
> including Mac external drives and old Apple 5.25 drivers to the back
> of it.

This arrangement was first implemented on the //c when Apple did
an upgrade on its ROM.  (They had to fix some problems related to
using 1200-baud modems anyway...)  I got to write the description
of the feature when I updated the //c Technical Reference Manual
around the middle of 1985.

You could daisy-chain <n> UniDisk 3.5s to the //c and access them with
ProDos.  While the software would permit up to 128 devices to be
included in the daisy-chain, power supply restrictions limit the
chain to seven devices.  The last device in the chain could be a
5.25" UniDisk (A 400K Mac external drive would probably also fit,
but I'd guess that you would need to much about with your own driver
routines if you want to read Mac disks).  Since a 5.25" UniDisk has
no connector for another device to be connected, that pretty much
follows.)  By the way, the port is not limited to connecting disk
drives.  (The logical extension of that statement is an exercise
left up to the reader.)

	seh