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From: morrist@ncrcae.UUCP
Newsgroups: comp.periphs,comp.sys.mac
Subject: Re: Making a Mac talk SCSI to a Sun
Message-ID: <2364@ncrcae.Columbia.NCR.COM>
Date: Mon, 16-Feb-87 09:42:45 EST
Article-I.D.: ncrcae.2364
Posted: Mon Feb 16 09:42:45 1987
Date-Received: Tue, 17-Feb-87 18:37:14 EST
References: <2594@phri.UUCP> <1784@hoptoad.uucp> <540211194.20192@minster.UUCP>
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Reply-To: morrist@ncrcae.UUCP (Tom Morris,x6376)
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Xref: watmath comp.periphs:209 comp.sys.mac:1325

In article <540211194.20192@minster.UUCP> martin@minster.UUCP (martin) writes:
>In article <1784@hoptoad.uucp> tim@hoptoad.UUCP (Tim Maroney) writes:
>>I believe there would be problems with having two SCSI masters.  A better
>
>No, SCSI (as opposed to SASI) was explicitly designed to allow any, or
>all, of the devices to be masters. If having two masters dosn't work, then
>one of the machines dosn't implement SCSI correctly (or completely!).
>
>I don't know about the implementations on the Sun, or the Mac, but all
>high performance (which I assume the Sun interface, at least is) interfaces
>should implement disconnect-reconnect to allow overlapped seeks, and
>this automatically gives one the multi-master capability (again so long
>as the software is not broken :-).

The real question is whether one or both of the SCSI devices can act
as both a Target and an Initiator. In every SCSI transaction, one device
acts as a target, and one acts an initiator. In the case of SCSI disk and
tape devices, the host acts as the initiator and the disk or tape controller
 acts as the target. In the case of host to host communication, at least one
of the devices (and preferably both) must be capable of acting as
a target as well as an initiator. Most SCSI protocol chips allow
both target and initiator operation. It does however, take significant
additional software to allow the target role to be used.