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C00002 00002	A DISPLAY TERMINAL SYSTEM FOR THE COMPUTER SCIENCE DEPARTMENT
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A DISPLAY TERMINAL SYSTEM FOR THE COMPUTER SCIENCE DEPARTMENT


	This is a plan to equip the Computer Science Department with
a system of keyboard and display terminals for use in teaching and
research.  The terminal system will make accessible to department
faculty and graduate students from their offices the IBM 360/67 in
the Computation Center, the PDP-10 in the Artificial Intelligence
Laboratory, and through the PDP-10 any computers on the ARPA
network that they may have made arrangements to use.  This includes,
for example, the ILLIAC 4 at Ames Research Center.  Connections to
other campus computers can also be arranged.

	In our opinion, such a terminal system together with suitable
hard copy output in the most important laboratory and teaching facility
that a computer science department can have.  The interests of the faculty
and students are too varied to be satisfied by any one computer since
no one computer will have all the hardware and software facilities that
are of research or teaching interest.

	The plan we are now proposing is based in part on a study made by John
McCarthy at M.I.T. in fall 1972 in support of a plan to get a terminal
system for Project MAC and the Artificial Intelligence Laboratory.
In this study, requests for proposals were sent to leading firms in
the display field and the replies were evaluated.  The best plan, however,
was found to be scheme being developed by Peter Wiener of Yale University,
and our plan is based on the Yale scheme which is also being followed by
the M.I.T. Artificial Intelligence Laboratory.  The Stanford Artificial
Intelligence Laboratory also hopes to upgrade its Data Disk display system
to the new standard.

	The goals that we want to achieve are the following:

	1. A terminal in each office used by faculty and graduate students.
This requires very low cost terminals.

	2. A large terminal facility for the use of students in courses.
About half the terminals would be available for this purpose.

	3. Each terminal should be capable of displaying at least half a
page of arbitrary character sets and also graphics.  The character sets
used in programming and in mathematics have proliferated to the point where
allowing each user to have whatever characters he wants is the only solution
compatible with the goal of using any computers that are available to our
faculty and students.

	4. Printing facilities compatible with the above should also be
available but not necessarily with each terminal.  In fact, there is no
present way of making such facilities available to each terminal but
suitable public printers can be had, for example the Xerox XGP.

	The scheme proposed has the following characteristics:

	1. The display image for each active user is stored as a 512x512
raster in an integrated circuit read-write memory.

	2. There are 64 terminals, but only 32 memories so that only half
of the terminals can be active simultaneously.  However, a low duty cycle
is to be expected if the terminals are in offices so this is ok.

	3. The cost to add a terminal to the system is about $500, and the
cost to add a memory is about $2200 now, but a large reduction is expected
in less than two years as 4096 bit memory chips come into production
replacing the 1024 bit chips on which the present prices are based.

	4. The system is controlled by a mini-computer, say a PDP-11,
which communicates with the host computers (initially the IBM 360/67 and
the PDP-10), and writes characters and pictures by directly addressing
the display memories.  The displays are maintained by a memory port that
reads bits from the memories into shift registers and transmits them
together with synchronization signals through a video switch to the
displays over coaxial cable.

	5. Each display is connected to the central unit containing the
memories by an individual cable, and the keyboards are connected to the
keyboard multiplexer by twisted pair unless it turns out to be feasible
to transmit the keyboard signal back on the same coaxial cable as is
used for the video.

	6. The video switch is a 32x64 electronic crossbar.  It will be
a copy of a unit now in use in the Artificial Intelligence Laboratory's
display system.

	7. In the initial version of the system all characters and vectors
are produced by software in the mini-computer.  A PDP-11/45 will take
150 microseconds in the worst case to write a character.  If the host
computers can support a higher rate of character writing then a special
character writer can be added.

	Here are the components of the proposed system and their estimated
costs:

	1. Integrated circuit raster memory complete with
buffer registers and power supplies					$73K
(based on prices paid by Yale and quotes to M.I.T.

	2. Keyboards							$14K
(70 keyboards at $200, based on quote by Microswitch)

	3. Monitors							$14K
(70 monitors at $200, based on quote by Ball Bros.)

	4. PDP-11/40 with 16K words private memory			$20K
(D.E.C. published prices)

	5. Shift registers and control electronics			 $5K

	6. Video switch							 $9K
(cost of video switch built by AI Lab)

	7. Keyboard multiplexer						 $8K

	8. Connection to PDP-10						$15K

	9. Connection to IBM 360/67					 $5K

						Total		       $163K

	Not included in these costs are engineering which we hope to do
with volunteer labor and wiring costs.

	Perhaps $50K of the costs can be obtained from projects.  The AI
Laboratory should pay for its connection and the cost of the terminals
used by project members on campus.  With NSF not giving facilities grants
any more, the outlook from that source is not bright.  We believe that the
University should pay the main cost as the major laboratory instructional
and research facility of the Department.