Delay Lines (Was: Univac I memory tank)

Dwight wrote: The Programma 101 indeed used a delay line. Such delay lines use magnetostrictive means to push a torque pulse into one end of the wire, as well as detect a torque twist at the other end of the wire. Magnetostrictive materials are typically a metal alloy that lengthens or shortens depending on the polarity of an external magnetic field, and will also generate a small magnetic field if stretched or compressed. In a magnetostrictive delay line thin strips of magnetostrictive metal are attached to opposite points tangential to the circumference of the end of a nickel-alloy(typically) wire. These strips, for whatever reason, are typically called "tapes". Each tape has a small coil of magnet wire surrounding it, wound oppositely around each tape, such that when a short current pulse is sent into the coils, one tape momentarily lengthens, and the other tape contracts, causing a slight but sharp twisting torque to be applied to the wire. This acts to transmit a pulse of energy into the wire. The torque twist mechanically travels through the wire to the other end, where it causes one tape to lengthen slightly, and the other to compress slightly, which induces a small current pulse into the coils around the tapes, which can be amplified to match the electrical characteristics of the original pulse. Sending a current pulse through the coils in one direction causes the twist to occur clockwise, and the pulse going the other direction induces a counter-clockwise twist, allowing ones and zeros to be pushed into the wire as clockwise or counter-clockwise torque twists. The amount of time that elapses (delay) from the pulse being injected to being received at the other end of the wire is based on the metallurgy of the wire, and its length. The wire is capable of remembering some number of torque twists as bits, with a clockwise torque, for example, representing a one, and a counter-clockwise twist representing a zero. The wire was typically arranged in a spiral inside a metal housing. Silicone or rubber supports supported the wire without attenuating the torque pulses in the wire. In some cases, there were "taps" along the length of the wire that used the same transducer method to pick off bits at different delay periods. The use of such delay line technology in calculators arose out of the need to store a moderate number of bits to represent the working registers of the calculator. At the time, magnetic core memory was still quite expensive, integrated circuit technology was in its infancy and too expensive to use for mass storage in a calculator, and it was generally cost and size prohibitive to store the bits required in discrete transistor flip flop storage registers (though a few very early electronic calculators did use this method). Given that delay line technology had been used with success on computers (though the Univac I delay lines were very different than magnetostrictive delay lines), they were a low cost, relatively simple way to provide the small amount of storage required for an electronic calculator. A prime example of the use of magnetostrictive delay lines in a computer was the Packard Bell 250, a low-cost "personal" computer introduced in the early 1960's. The bit-serial nature of the delay line was ideal for a calculator, since a bit serial architecture is coincident with the most efficient way to make an electronic calculator, where raw speed is not a requirement, and minimizing the component count saves money. The serial nature of the delay line means that if a specific bit is needed, the logic must wait around for the bit to arrive at the end of the delay line. This slows down the operation of the device, but in the case of a calculator, where results are subject to human perception, 10s to 100's of milliseconds is well within the acceptable time for a calculation to occur. lines. One was for registers and the other was for lookup tables that loaded at turn on time from a metal tape ( as I recall ). The Diehl Combitron did use two separate delay lines, one for the registers(as well as learn-mode program storage) as mentioned, but the other one wasn't really for lookup tables, but instead stored the operating microcode that made the machine run. The microcode was indeed loaded from a punched metal tape at power-on time. The ingenious design of the Combitron was done by Dr. Stanley Frankel, a nuclear physicist who was deeply involved in the mathematical modeling that made the atom and hydrogen bombs possible. After the Manhattan project ended, he was involved in the design of quite a few computers and calculators. Notable computers that he designed were the Librascope-General Precision LGP-30, the aforementioned Packard Bell 250, and some design work on early General Electric computers. He also designed the Smith Corona/Marchant Cogito 240 (and follow-on Cogito 240SR) electronic calculator, as well as the Diehl Combitron. Many calculator companies used magnetostrictive delay line technology for storage in their earlier calculators, before the time that integrated circuits took over the storage duties. They included Friden(Singer) (all of their in-house designed machines used delay lines, e.g., 130, 132, 115x, 116x), Canon(which made machines for Monroe), Wyle Laboratories (WS-02 and Busicom 202, 207 and 2017), Olivetti (Programma 101 & follow-ons), Sony(early Sobax), Victor(1400-series), Monroe(EPIC 2000/3000, 820/820A), Diehl(which made machines for SCM and Victor), and Olympia. -Rick -- Rick Bensene The Old Calculator Museum http://oldcalculatormuseum.com