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From: info-vax@ucbvax.ARPA
Newsgroups: fa.info-vax
Subject: microVAX III and busses
Message-ID: <7746@ucbvax.ARPA>
Date: Mon, 3-Jun-85 19:27:51 EDT
Article-I.D.: ucbvax.7746
Posted: Mon Jun  3 19:27:51 1985
Date-Received: Wed, 5-Jun-85 01:18:15 EDT
Sender: daemon@ucbvax.ARPA
Organization: University of California at Berkeley
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From: sasaki@harvard.ARPA (Marty Sasaki)

I find the rumors about things truly amazing, especially the microVAX
III. A recent note mentioned that the next microVAX will not have a
Q-bus, but might use a CI or a UNIBUS. This is very unlikely.

The Q-bus is a pretty fast bus, almost twice as fast as a UNIBUS in
practical applications and use. It has a 22 bit address space compared
to the UNIBUS' 18 bit space, which means that mapping from bus space to
real memory is easier with a Q-bus. Peripherals are also cheaper on a
Q-bus. There is no reason to use a UNIBUS over a Q-bus.

The CI bus is meant to be a communications channel between processors.
It talks a magic protocol and runs at 70 meg. The cost of a CI
controller (~$20k) is more than the base microVAX II configuration. It
doesn't make a lot of sense to spend more money on the CI controller
than on the computer system.

I don't know what the microVAX III will be like, and I don't think that
DEC does either. Yes, there are several VAXen in the works (there always
are), and at least one has to be microprocessor based, but as far as
something close enough to being a product to be called a microVAX III? I
doubt it.
----------------
  Marty Sasaki				net:   sasaki@harvard.{arpa,uucp}
  Havard University Science Center	phone: 617-495-1270
  One Oxford Street
  Cambridge, MA 02138