Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!nrl-cmf!ames!pasteur!ucbvax!hplabs!hpfcdc!hpfclm!kinsell
From: kinsell@hpfclm.HP.COM (Dave Kinsell)
Newsgroups: comp.periphs
Subject: Re: SCSI interfaces
Message-ID: <1600004@hpfclm.HP.COM>
Date: 26 Jan 89 16:37:22 GMT
References: <1138@naucse.UUCP>
Organization: Hewlett Packard -- Fort Collins, CO
Lines: 23


>> I have heard (I can't remember where exactly), that > Apple's use of the
>> SCSI is somewhat non-conforming to the standard.

>The MAC computers use a 25-pin DB25 (RS-232C style) connector instead of
>the standard ALT-2 50-pin, but other than that, I am not certain of how
>they vary from ANSI. 

Mac uses a DB25 at the computer, but sometimes adapter cables are used
to convert to Alternative 2 connectors at the peripheral.  Some of the
ground wires are sacrificed in this scheme.  Alt 2 connectors are what
some people call Centronics style, but with 50 pins.  AMP calls them
"Champ" and Amphenol calls them "Microribbon".

I've seen discs sold for Mac that use DB25, and others that use Alt 2
connectors.  External peripherals sold for SUNs typically use DB50
connectors.  I don't know if that was an attempt to lock out competition
with non-standard connectors, or if they predated development of the Alt
2 recommendation in Appendix D of the SCSI standard.  The Mac approach
was most likely used to save back panel space.

-Dave Kinsell
 kinsell@hpfclm.HP.COM