Tektronix terminals [was: Re: Re: Humpty Dumpty]

Rick Bensene rickb at bensene.com
Sat Feb 10 16:19:25 CST 2007



>>> There also was a 'write through' mode,
>>> again, not sure if it was a hack, or part of the production
terminals,
>>> that would (within the limitations of the RS-232 port) could do
simple
>>> dynamic (non-stored) vector graphics.

>>It is also on the 4010.  The 4010 and the 4014 have a card cage into
>>which you can insert your own cards.

>I have a 4010 and didn't see any mention of this in the manual.  Do you
>know if it took special cards?

I know that the 4010 did not provide write-through in "stock" form.
There were only two aspects of the 4010 that did write-through.  One was
the "crosshairs" that would be drawn on the screen when the "GIN"
(Graphic In) escape sequence was received.  When put into GIN mode,
write-through X&Y crosshairs would appear, and two thumbwheels could be
used to position the intersection of the crosshairs anywhere on the
screen, then any key could be pressed to send the coordinates, and the
key pressed, back to the host system.  The other was a write-through
vertical line that scanned left-to-right when the optional dry-silver
paper hardcopy unit was connected to the 4010.  The write-thru line
would "scan" the screen, and areas of the screen that had stored
points/vectors would cause voltage variations in a sense circuit, which
would cause a special CRT in the hardcopy unit to duplicate the screen
contents as dry-silver paper would pass by the CRT.  Then, the paper was
passed through a heater (HOT!) that would develop the latent image in
the silver, and fix it.

There very well could have been options or hacks that provided the
ability to draw write-through vectors.  I do know that there was a
PDP/11 DMA parallel option that was available for the 4010 that allowed
much higher speed operation than offered by the serial port, but there
were handshaking considerations that had to be taken into account,
because the PDP/11 could easily outpace the ability of the 4010 to keep
up.  I do know that there were write current adjustments which you could
fiddle with which would turn down the energy of the beam enough that it
wouldn't cause storage.  But then, the 4010 was write-through ONLY.  It
became really difficult to read text on the screen, as it would have to
be continuously refreshed.  Through the serial port, there just wasn't
enough speed to be able to refresh a whole screen's worth of text fast
enough to be readable.

I believe that the statement that was made that the 4014 (a large-screen
[19" diagonal, IIRC) version of the 4010, with faster vector draw rates,
and more features) is correct.  I think that the 4014 did have a
programmable write-through mode but I recall that it was an option, and
didn't come standard.

I remember talking to someone in the CRT fab building (Tek built all of
their own DVST and oscilloscope tubes for many years -- the building no
longer exists on the campus though..it was demolished quite a number of
years ago) who was involved with the design of the DVST tube for the
4014.  It was a major challenge.  It was a large screen for the time,
and major challenges involved in structural stability, along with the
difficulties of fabricating the complex structures that made the storage
tube possible.

Tek's DVST terminals were mainstays of graphics display technology for
quite some time.  It was much less expensive than the vector systems
made by folks like Sanders and others.

I remember a CAD system in the basement of building 50 that was
PDP-8-based, made by a company that I can't remember, unfortunately.
The company OEM'd Tek's storage tubes for the displays on the machine.
The system was used for circuit board layout.  It didn't do routing or
anything like that...it only allowed a layout to be "drawn", and then
turned into a photoplotter tape that would generate the negative artwork
for the board.  The storage tubes on this system definitely operated in
write-through mode most of the time, and were capable of having quite a
few vectors on the screen at once without too much flicker.   I spent
quite a bit of spare time down there watching the artists (in those
days, circuit board layout folks were truly artists) designing the
various layers of Tek's famous multi-layer circuit boards used in their
oscilloscopes and other instrumentation.  The PDP-8 was a transistorized
PDP 8 (not a straight-8 but one of the later ones before they started
using ICs), and had a couple of RK05 drives, along with a full rack that
was filled with the display subsystem electronics.

Tek later made a machine called the 4081.  It used a similar DVST tube
as the used on the 4014 terminal.  It was a computer workstaiton based
on an Interdata 8/16 CPU that Tektronix OEM'd from Interdata.  The
machine had a Tek-designed custom display-list processor, and could do
some pretty fancy write-through graphics, along with storage graphics.
It was fast enough that even a reasonable amount of vector text could be
painted on the screen in write-through mode.  Storage and write-through
could be mixed.  The machine used what I believe were OEM'd from Diablo,
similar to RK05-F's, with one fixed platter, and one removable platter.
The machine also had a cartridge tape drive that could be used to "IPL"
the system.  I spent a lot of time writing Pascal and machine-level code
on this machine.  There were some really fun games that were written for
this machine.  There was a disk operating system (I can't remember the
name) that was kind of OS/8-like, with similar commands, and
user-perceived filesystem structure.  I wonder if any of these machines
are still around an in operation.   

After the 4081, the move to raster graphics had gathered speed.  Tek did
a lot of research internally on raster graphics.  There was an
absolutely groundbreaking machine called the Magnolia (never marketed)
that had some kind of bit-slice processor, a highly capable bit-slice
raster BLIT graphics engine.  The machine had a Micropolis 40MB 8" hard
disk in the base of the "terminal", and ran a Tek-developed window-based
multiprocessing (Unix-like) operating system, with the development
environment being Smalltalk.  It had a monochrome display, but could do
gray-scale, which made shading, etc. possible.  The biggest problem with
the design was that with the hard disk in the base, users tended to kick
and bump their feet on the bottom of the pedestal, which would cause
shocks to the hard disk, and cause head crashes.  Those old drives were
pretty sensitive.  The sad part of the whole thing was that Tektronix
never pursued these machines as a product - the machine never made it
past prototype stage.  I believe that Xerox Parc had their early
machines (Star, etc.) out already, which the Tek machines were clearly
patterned after, but Tektronix' graphics expertise would have made these
machines into tremendous standalone graphics workstations long before
they became mainstream.  An example of one of many of Tektronix' missed
market opportunities.

I ended up getting a number of those Micropolis 40MB drives (brand new
in the box, for something like $20) used in Magnolia from the Tek
Country Store (another whole article could be written on this wonderful
place) much later, and built a custom interface for a homebrew
6800-based computer that I'd built, and wrote drivers for the FLEX
operating system to talk to the drive.  The drives ran quite hot, were
extremely noisy, and had essentially a simple parallel interface.  It
was pretty cool having a computer system at home that had a whopping
40MB of hard disk space when everyone was running Apple II's and the
likes with floppies.

As always, a long diatribe that somewhat wanders off-topic, but it is
all definitely within the context of the list.  

Rick Bensene
The Old Calculator Web Museum
http://oldcalculatormuseum.com






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