Asri-unix.1381
net.works
utzoo!decvax!cca!CAULKINS@USC-ECL@sri-unix
Sun May 2 23:41:22 1982
Cost Driven Architectures
I (Dave Caulkins) am the manager of the data processing facilities for
a small SF Peninsula startup; we have a V7 UNIX running in an Onyx and
a CP/M based system running in a Dirac, manufactured by Molecular
Engineering. It's this last machine I'd like to talk about. Its
architecture is interesting - a 34MB hard disk with a smart
controller, talking to up to 32 Z80-with-65K-RAM processors via a
parallel CSMA bus. See the Dirac Description below for detailed size
and cost numbers. Each user gets his own processor and 65K, and in
consequence adding users doesn't degrade performance nearly as much as
in a system in which one central processor dances around among 8 - 32
users. We've done some loading studies, and under medium load
conditions (15 users all working with files >65K via an editor) the
users-vs-response-time curve is almost flat. Under high load
conditions (each user requsting a large number of disk accesses per
second) the curve is roughly linear from 3 out to 15 users.
The Dirac doesn't quite make it. CP/M is nice in that there is a
great deal of 3rd party software available, some of which is good
quality (caveat emptor !). The CP/M file structure is painfully
primitive and hard to work with.
I think an attractive architecture would be as follows: A UNIX based
multiprocessor with 68000-and-512K per user, with 80 - 160 MB of
common hard disk available to all users. The 68000-and-512K ought to
be doable for less than $2K. Such a system should offer a very
attractive multi-user work station environment for a lot less than
CEI, Fortune, or others of the $5K standalone UNIX workstation flavor.
Standalone devices have a significant part of their cost in the case,
keyboard, CRT, and other non-computer elements. The terminal
manufacturers are beginning to do reasonable designs and realize good
economies of scale; seems to me that the natural division between
workstation terminal and computational resources offers real cost
adavantages.
Does anyone know of a company that has or is planning a system like
this ?
Dirac Description
Cost: $15K for the basic box - 34MB disk, disk controller, power
supplies, 8" floppy drive and slots for 32 Application Processors
(APs); one required for each user. APs cost $1K each, less in
quantity. The AP price is rather high - manufacturing cost is
certainly well under $200.
Size: basic box - 24" high x 12.5" wide x 31" deep.
AP - 4" x 9"; 44 ICs
This may be where Dirac went astray. They put a lot of effort in
making the system quite small; the AP board is very tight. I for one
wouldn't mind a system 2X or 3X as big, but with the enhanced
capability discussed above.
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