The Tektronix 4010 series was a family of text-and-graphics computer terminals based on storage-tube technology created by Tektronix. Several members of the family were introduced during the 1970s, the best known being the 11-inch 4010 and 19-inch 4014, along with the less popular 25-inch 4016. They were widely used in the computer-aided design market in the 1970s and early 1980s.

thumb|A map of the contiguous United States on the Tektronix 4010. The typewritten note at the bottom of the display bezel warns against [[screen burn-in]]

The 4000 series were much less expensive than earlier graphics terminals, such as the IBM 2250, because no additional electronics were needed to maintain the display on the storage-tube screen; images drawn to the screen remained there until deliberately erased. This eliminated the need for computer memory to store the images, which was expensive in the 1970s.

The display series remained popular until the introduction of inexpensive graphics workstations in the 1980s. These new graphics workstations used raster displays and dedicated screen buffers that became more affordable as solid-state memory chips became markedly cheaper.

History

thumb|upright|The Tektronix 564 [[storage oscilloscope used the same technology which was fundamental to the 401x series of graphical computer displays]]

The Tektronix direct-view bistable storage tube was first used in the Tektronix 564 oscilloscope in 1963, and was first used for non-oscilloscope applications in the 601 monitor in 1968. A number of graphics terminals based on this tube and others from the 600-series were developed, including the Advanced Remote Display Station from MIT's Project MAC, and the KV8I (later, KV8E) from Digital Equipment Corporation using the 11-inch diagonal 611. These displays consisted of just the CRT and related basic electronics; it was up to software on the host computer to produce a display by driving the CRT signals directly.

Tektronix decided to enter the computer terminal market themselves, introducing the 4002 in 1969, and the updated 4002A in 1971. The latter sold for , and required a host adaptor. These were similar to the earlier third-party terminals, essentially combining one of their storage tubes with the circuitry needed to decode instructions from the host and turn those into control inputs. However, the 4002 had the unique feature that only a portion of the screen was a storage tube, with a small section set aside for normal refresh-based drawing. This area was used for status messages and entering commands. As they did not include raster scan hardware or any form of memory, refreshing this area rapidly enough to reduce flicker was up to the host computer.

Starting in 1972, the 4002 was first supplanted and then replaced by the 4010. A number of changes and simplifications allowed these to be far less expensive, initially released at and another for a host adaptor. Other models in the 4010 series included the 4012 which added lower case characters, and the 4013 with an APL character set. These were implemented using plug-in boards that could be added to the base-model 4010 as well. In the 1980s, a version using a built-in RS-232 port and a number of missing features was released as the 4006, which was small enough to fit on a desk, selling for .

A wide variety of peripherals were available that worked on some or all of these models. The first line, introduced with the 4010, included the 4610 Hard Copy Unit, an early graphics printer. This used a system in the monitor to scan the display line-by-line, which sent signals to the printer where a one-line-tall CRT duplicated the image on thermal paper. Normally selling for , a version allowed the printer to be shared among four terminals. The printer adaptor could be pre-installed in the 4010, making it the 4010-1, and it came pre-installed on both the 4012 and 4013 which do not appear to have used the -1 notation to indicate this. The 4631 was a version of the 4610 with a sheet feeder and higher speed.

A properly equipped 4014 could also drive a pen plotter through an expansion card, including the GPIB-based 4662 Interactive Digital Plotter and 4663 C-sized version. Plotters offered color graphical output via colored pen selection, which could be embedded in the graphics data.

For storage, the systems could write out the data stream of characters as they were received from the host, allowing them to be played back locally to recreate the display. Storage options included the 4911 punch tape, the 4912 using cassette tapes based on a Sykes TT120 mechanism, and later added the 4923 based on the 3M DC300 digital tape system.

Other devices in the lineup included the 4901 and 4903 Interactive Graphic Unit, which drew crosshairs on the 4002 (this capability was built into the later models), and the 4951 Joystick. This hardware allowed the user to select any point on a display, and to input its coordinates to a computer, allowing support of a CAD system.

thumb|Tektronix 4051

The 4010 series was also used as the basis for two self-hosted systems. The Tektronix 4050 series used the 4010 or 4014 with internal processors and a DC300 tape unit to produce a simple desktop unit. There were three models: the original 4010-based 4051 with an 8-bit processor, the 4052 with a 16-bit processor, and the 4054 which combined the 4014 screen with the 4052 logic. The 4081 was a version with an Interdata 7/16 minicomputer built into an office desk, which saw limited use. Tektronix continued selling the basic storage tubes to OEMs, the 19-inch version as the GMA101 and 102 (the former offering roughly twice the drawing speed) and the 25-inch as the GMA125.

Tektronix also sold a set of graphics software routines in FORTRAN known as PLOT10 that converted simple inputs like lists of numbers into a graphic display such as a chart. Another common solution was the DISSPLA software system, which was adapted to run on the 4010.

The command format for sending graphics to the terminals was very simple, and was soon copied by a number of other terminal vendors. This de facto standard for encoding graphical information was later ported to traditional video terminals using raster scan displays, although these generally offered lower resolution, perhaps half that of the 4010. A number of these emulations also understood the color codes from the Tektronix 4105 raster scan terminal, which added color to the original 4010 command set. This graphical data standard continues to be emulated by newer terminals to this day; NCSA Telnet and xterm can emulate the 4014 (<code>xterm -t</code>).

Principles of operation

Conventional modern video displays consist of a series of images, or frames, representing single snapshots in time. When the frames are updated rapidly enough, changes in those images provide the illusion of continuous motion. Computer displays, where the image is generally static for extended periods of time (for example, a page of text), required a stationary, more-precise, flicker-free image, as compared to television displays available at the time. A modern solution is to use additional hardware and computer memory to store the image between each update, a section of memory known as a framebuffer.

In the 1960s, memory based on core was extremely expensive, generally priced in dollars or cents per bit. Solid-state memory was even more expensive, and could only be used for a handful of high-speed working storage registers in data processing hardware.

If one wanted to store a screen of text at 80 columns by 25 lines and using 7-bit ASCII, one would require 8025 = , making the price of the terminal prohibitive. The cost would be even more if the terminal needed to display graphics. For instance, a graphics terminal supporting 1-bit points (on/off) at resolution would require 1024768 = of memory, likely more than the cost of the computer it connected to. One solution to reduce the amount of memory required was to represent the image not as dots, but straight-line "vectors". In this case, only the endpoints have to be stored in memory, and additional hardware draws between them to produce the display. A coordinate within that same 1,024 resolution space requires (2<sup>10</sup>), so if a display can hold 1000 vectors in total, it requires per end = . The IBM 2250 graphics terminal used this solution, and sold for .

Tektronix had originally developed their storage tubes in the late 1950s as a way to store images on oscilloscope displays for study, although the same system had already been used in radar displays. The basic concept used a conventional CRT layout, but with two sets of electron guns. One, the flood gun, provided a constant flow of low-energy electrons covering the entire screen, causing it to glow faintly. The second source, the write gun, resembled the normal gun of a black and white TV, and its beam was moved about on the display surface in the conventional fashion by using electromagnetic coils.

The storage tube technology was vulnerable to screen burn-in, as the continuous flow of electrons illuminating a stored image gradually degraded the light-emitting phosphors over a long period of time. To reduce the rate of display degradation, the hardware was designed to blank the electron beams after a period of inactivity on the screen. Software screensaver programs were not useful in protecting storage tube display screens from burn-in of images.

Also, complex and precise images would gradually become more diffused and blurry, as the stored charges on the phosphors slowly migrated and diffused away from their original locations. The only way to correct this gradual blurring was to erase and redraw the entire screen.

Because the display tube itself stored the image, there was no need for any sort of auxiliary graphics memory, greatly lowering the cost of the terminal. The 4010 cost $3,950, almost two orders of magnitude less expensive than IBM's competing graphics displays. This made very complex and detailed computer graphics practical for a much wider audience. The Tektronix approach also had the advantage that there was no limit to the number of vectors that can be displayed; one could simply keep adding them to a complex image, whereas a solution like the IBM terminal had a limited number of vectors it could refresh on its display. Early CAD systems made by companies such as Computervision took full advantage of the graphic storage capability, and were able to display arbitrarily complex designs without annoying flicker.

The main disadvantage of storage tubes was that once an image was stored, it could only be removed by erasing the entire image. This made such screens unsuitable for working with scrolling text, animation, or any other display where portions of the image were continuously changing. Some early CAD workstations employed both a video terminal to display frequently changing text, and a Tektronix display showing complex graphics images.

Tektronix introduced the write through concept for non-stored vectors, but with the terminal itself lacking any memory, the data had to be continually refreshed from the host computer. The communications speed of the connection between the terminal and host limited the number of refreshed objects that could be supported, and was often in the range of a few dozen graphic elements. Another disadvantage is that it required a brief interval for the image to "store" on the display screen, which limited the maximum speed with which the image could be drawn. Tektronix referred to this as the stored writing speed, and measured it in terms of vector-inches-per-second, with ratings between 1500 and 4000 being typical for their displays.

Notes

References

Citations

Bibliography

  • Tektronix 4010-1, video of a 4014-1 executing an example file created by the Skyplot program
  • tek4006, shows a 4006 being used in text mode as a terminal on an Ubuntu server along with a number of Tek demos being drawn
  • Hvosm spin001, an animation of a vehicle collision rendered frame-by-frame on a Tektronix 4006
  • Tektronix 4010- 4014 Graphics 3D Vintage Computer, data plotting on a 4010-4014, mostly using the Disspla software package