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From: leichter@yale-com.UUCP
Newsgroups: net.unix-wizards
Subject: Re:  Advice on VAX peripherals wanted, note re HSC50
Message-ID: <2723@yale-com.UUCP>
Date: Mon, 16-Jan-84 14:50:08 EST
Article-I.D.: yale-com.2723
Posted: Mon Jan 16 14:50:08 1984
Date-Received: Fri, 20-Jan-84 06:59:34 EST
References: utcsstat.1633
Lines: 13

A HSC50 contains multiple F-11's; these are the chips in both the 11/23
and 11/24, which differ in the backplane:  11/23 is Q-bus, 11/24 is Unibus.
(Actually, to be complete:  11/23 is 18-bit Q-bus, 11/23+ is 22-bit Q-bus.)
It isn't particularly meaningful to ask whether the F-11's inside an HSC-50
are "11/23's" or "11/24's".

While the DSA protocol may be complex, it has two advantages over usual
disk-driver interfaces:  It looks like a fairly high-level network protocol,
not a series of random read-only, write-only, and read-write bits plus
interrupts and timing constraints; and it is done, once and for all:  New
disks can connect to the HSC-50 without the host talking to it knowing that
they are new...the HSC-50 protocol stays unchanged.
							-- Jerry