Forrester and his "Whirlwind"

Background to the creation of tube computers - Whirlwind ("Whirlwind")

In 1943-1944 there was a need to develop a universal simulator that could simulate the flight of an aircraft in real time. This would enable pilots to improve their skills, while designers can study the effect of changes in the possible tactical and technical characteristics of new models. Until that time, there were such simulators (based on analog electromechanical engineering), but they were not universal, that is, they were suitable only for a specific design of the aircraft.



Creating a universal simulator would help save on design and training.

The Massachusetts Institute of Technology has become one of the centers where American air defense systems have been improved. At the end of 1944, work on the creation of such a simulator began at MIT; the Servo Mechanism Laboratory became the executor of the project. Jay Forrester led the ASCA project; Robert Rievers Everett, Master of Electrical Engineering, became an assistant.
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airplane simulator

Together with a group of employees, they worked half a year to create an electromechanical analog simulator. Electronic analogue technology in real time gave low accuracy of calculations, was not able to solve simultaneously hundreds or more differential equations with many variables, and, therefore, did not match the customer's TZ, and simple operations required a long fuss with punched cards or punched tapes.




It was necessary to look for a new solution to the problem.

Perry O. Crawford, Forrester's colleague, largely contributed to the birth of the BT machine ... ... he told me about the Harvard Mark I car and ENIAC, which was still in the design stage. Perry was very open, devoid of bureaucratic manners and easily communicated with naval commanders, although he himself was a civilian. He suggested to them that digital computers in the future should be used at command posts as the basis of information and management systems ... We owe him in many respects the birth of our machine s. "

Work began on the creation of the machine, which was given the name "Whirlwind" to emphasize its speed. Employees started developing a draft version of a digital machine (the customer was not notified of such a turn of events). Forrester and Everett got acquainted with the structure of Mark I and ENIAC, consulted with their developers, studied the “First version of the EDVAC report” (Neumann) and began to “model” the car from scratch.

In 1945, Forrester appealed to the leaders of the SDD. He suggested that they create a simulator no longer on coarse analog computing devices, but on the basis of a digital computer. It was a difficult job to create a computer that could work in real time.

It was necessary to increase its speed up to 20-50 thousand operations per second, to use reliable internal memory of large capacity, to create software for processing the incoming data flow, to increase the reliability of the machine. The main difficulty was that people who had no experience in working with digital computers had to address this issue.

Work began on creating an internal memory that would satisfy the requirements of the project, and for this it was necessary to increase the reliability of discrete lamp circuits. The main memory of the EDVAC computer, which consisted of 32 mercury ultrasonic delay lines (RULZ), was not suitable for a new project because of its slowness. Forrester tried to use gas-filled lamps (“neon”) and xenon flash lamps to store a single discharge. In early 1947, English scientists began using a standard cathode-ray tube (CRT) to create an internal memory, which made it possible to store a single binary digit on the screen and read it. For four years, MIT employees worked on the design of the tube, the diameter and uniformity of the spot on the tube screen was stabilized, the focusing was improved, and an additional electron beam gun was used to periodically regenerate the electrostatic charge.


RULZ

Work was underway to increase the reliability of lamp circuits. Until that time (as is known) thousands of lamps were used in lamp machines, but the “vital activity” of such a lamp was 500 hours, and this would lead to a machine malfunction every couple of minutes. The life of the lamps has been increased. In 1947, a multiplying device was developed, which contained 4 hundred lamps, for multiplying two 5-bit binary numbers. Everett wrote "... the device worked continuously for many days, and we checked each result with the correct answer. Of course, it failed, but we noticed that in most cases it was 3:00 pm. It turned out that at that time the cleaner in the next building entrance included a freight elevator and an additional load on the local power grid arose, this led to failures. It was decided to use a separate motor-generator system to power the machine, the inertia of which provided protection from peaks voltage arising from the connection of additional equipment ... "



Later, another problem arose that required a solution. The sponsor has changed (OSRD and SDD ceased to exist, and they financed this project), the cost of a project to develop such a computer was constantly increasing. “Whirlwind” was planned to be created in two years, with a budget of 875 thousand dollars, but the cost of the project increased to 3 million dollars (which was 65% of the total budget of the mathematical department). To justify such an expenditure of funds Forrester prepared a report for the Pentagon, in which he described where such a control computer could be used. But still, instead of the requested $ 1.5 million per year for the project, Forrester and his project were allocated only $ 250,000. The project was saved by a new sponsor - the US Air Force (this happened in 1949, when the Americans learned that an atomic bomb was tested in the USSR). The project to create a computer "Whirlwind" was approved by the Pentagon and allocated the necessary amount for its completion. In March 1951, the machine was fully assembled, debugged and executed the first large program written in assembler by John Gilmore, put into operation in April of the same year, and Forrester headed the created laboratory of digital computer technology at MIT.

Computer "Whirlwind"

Almost $ 5 million was spent on development, it was based on the classic Princeton architecture, but a common bus was used to exchange information between the machine units. The diode array was used to control the sequence of operations in the computer, the signals from the clock pulse generator went to certain inputs of the array, and its output signals opened the keys, which were used to select the code of the desired command that entered the corresponding control device register. The length of the machine word was limited to 16 binary digits, including the sign of a fixed-point number, subroutines for working with floating-point numbers and a double-length word.

The car housed 5,000 lamps (mainly pentodes), 11,000 crystalline diodes, it consumed 150 kW of energy, the weight of such a computer was 10 tons, the occupied area was almost 950 square meters. m

The vortex was a unicast, synchronous action with a clock frequency of 1 MHz, a machine with an internal memory that contained 32 modified Williams tubes with a capacity of 1K words. A group of 32-bit registers built on mechanical keys and 5 electronic registers served to test the memory operability.

Punched tape and reading device were used to enter data and programs in the computer. CRT with a diameter of 40 cm served as a display. The data was entered into the machine on a tape punched by a flexorayer. And the results were displayed on the CRT screen or displayed on the same flexoriter.
The cathode-ray tube was similar to a television, a large electron-vacuum tube in which a beam of electrons, falling on the phosphorus-coated inner surface of the screen, caused it to glow. The speed of the machine was 20 thousand operations per second, the addition operation was performed in 49 μs, and multiplication in 61 μs.

The whirlwind computer was modernized and the number of lamps increased to 12.5 thousand, and the diodes to 23.8 thousand, the car occupied two floors in one of the MIT buildings. On one were the tape drives and devices for communicating with objects. Part of the machine, internal memory and control panel are located on the other, in the basement there was a power unit (power 150 kW), an air conditioner was mounted on the roof of the building.

The maintenance of computer memory cost 32 thousand dollars a month (one tube cost about 1000 dollars), so Forrester was looking for a replacement for CRT. In 1951, the first sample of memory on ferrite cores was created, which two years later replaced the memory with a CRT. The speed of the computer doubled, the addition operation took 8 μs., Multiplication -25.5 μs., Division - 57 μs.


memory on ferrite cores

Five tape drives (with a capacity of 125 thousand words each and a reading speed of 390 words per second) and two drives on magnetic drums (with a capacity of 2048 words and a rotation speed of 60 rev / s, the speed of write / read operations — 31 thousand words per second).

To play letters, numbers, topographical signs and other symbols on the luminescent screen, Charactron tubes were used (as displays). An opaque plate with a set of pinholes in the form of depicted characters served as a stencil with which the symbols were formed on the screen. The software of the machine allowed the computer to solve several tasks simultaneously, working in the time-sharing mode.

Direct Memory Access (DMA) method : the input data was updated every 15 seconds and recorded on a separate track of one of the magnetic drum drives, after which the unit was transferred to the internal memory (the calculation process was continuous).

The vortex was a prototype of a whole range of computers that allowed the creation of a powerful US air defense system, SAGE, a semi-automatic system that can simultaneously process data from 23 regional centers in the USA and Canada, while serving a giant network of radars and other detectors.



It looked like this: the operator in each district center entered data on the keyboard, looking at the round screens, where weather conditions, the trajectory of the aircraft, information necessary for the operation of the air defense system were displayed. SAGE I / O devices maintained continuous communication between neighboring centers via telephone lines. About 8-12 billion dollars was spent on the creation of SAGE.


the workplace of the operator of the first national air defense system of the USA - SAGE

Work on the project "Whirlwind" gave invaluable experience to its creators and developers. Many of them have held senior positions in many well-known companies: Kenneth Olsen founded the Digital Equipment Corporation (DEC) corporation in 1957 and was engaged in the production of mini-computers.

Forrester himself remained the head of the department even before 1956, and later devoted himself to researching the dynamics of production, as well as world social and economic processes, and became the founder of a new discipline - system dynamics. Everett and Forrester were awarded the National Medal for Technological Achievement, the highest government award for United States engineers.