Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!wuarchive!decwrl!shelby!neon!kaufman
From: kaufman@Neon.Stanford.EDU (Marc T. Kaufman)
Newsgroups: comp.sys.mac.hardware
Subject: Re: Sharing the SCSI bus?
Message-ID: <1989Dec5.165138.5192@Neon.Stanford.EDU>
Date: 5 Dec 89 16:51:38 GMT
References: <1989Nov29.030959.27969@Neon.Stanford.EDU> <8252@pogo.WV.TEK.COM>
Sender: USENET News System <news@Neon.Stanford.EDU>
Reply-To: kaufman@Neon.Stanford.EDU (Marc T. Kaufman)
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Organization: Computer Science Department, Stanford University
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In article <8252@pogo.WV.TEK.COM> daveb@pogo.WV.TEK.COM (Dave Butler) writes:
>I'm finding this discussion of Apple SCSI quite interesting.  I've been trying
>to determine the differences between Apple SCSI and ANSI SCSI.  So far, I've
>been told that Apple SCSI doesn't use the ATN line.  Is this true, and if so,
>how does the initiator send messages?

The ATN line is usable (note that I didn't say "used").  The MacOS provides
a SelectWithATN command, but only allows 1 byte to be sent before ATN is
negated - thus precluding IDENTIFY.

>how does the initiator send messages? Also the book "Inside Macintosh Vol IV"
>states on page 286 that Mac implements both arbitration and disconnect /
>reselection; I find it disturbing to find out that this is not so. 

I had never noticed that.  You're right, it does.  They lied.

>anyone please tell me the specific differences between Apple and ANSI SCSI, as
>well as any other "gotchas" (like not implementing arbitration, when the
>documentation says otherwise)?  

>    PS. If there is an actual document with this information, I'd love to
>    know its name, and how to get it.

I suggest "Mac Nosy" by Jasik Designs.

Marc Kaufman (kaufman@Neon.stanford.edu)