terminals, simple 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