History and Evolution of 1100/2200 Mainframe Technology • UNISYS This paper was prepared in recognition of the 35th anniversary of USE inc. and was presented at the Fall 1990 Conference in Seattle, Washington. Copyright© 1990 Unisys Corporation All rights reserved 006499-12PETSCH- BJH Printed in U S America ~. History and Evolution of 1100/2200 Mainframe Technology • UNISYS November 8, 1990 Richard J. Petschauer HISTORY AND EVOLUTION OF 1100/2200 MAINFRAME TECHNOLOGY INTRODUCTION used to solve such a wide variety of problems. However, it also required a new class of 'Phis paper covers the highlights of the history technology that the earlier calculators did not and evolution of the Unisys 1100/2200 Series need-a means to store the sequence of processor and memory technologies. The operations, or instructions, to be performed period covered spans the last 35 years and and also a place to hold the input data and the includes the recent product announcements in results. This function of "memory" presented 1990. A number of articles have already a large problem in the early days of covered the earlier years including the computers. The memory used a different computers that were developed then. Others technology than the logic for the processor, reviewed the formative time of the Eckert and the two developed on separate but Mauchly and Engineering Research Associates parallel tracks, which to some extent still (ERA) companies and their joining Remington continue today. For quite a few years, until Rand which later merged into the Sperry the mid 1970s when the semiconductor Rand organization. Still others have traced memory became so capable, memory the architectural aspects of the 1100 Series. technology greatly affected the performance, This paper instead concentrates on the capability, and cost of the computer system. internal logic and memory technologies used in the 1100/2200 systems and some of the Early in the memory technology development, industry factors present during this time. a split occurred. One technology family was developed for the program and internal data These early machines originated during a needed by the computer-which required fast period when computer designers were access; and another was developed for less searching for better ways to best do the basic frequently used data which needed to provide functions of computing and memory. This larger capacity storage at a lower cost. This computing, or logic technology as we will call "external" storage class, mostly represented it, had a time lead over that of memory since today by disk and tape storage, has seen it had been used in early digital calculators dramatic improvements over the years. and some control equipment. However these However, it is beyond the scope of this paper machines were special in nature since their which will concentrate on the central inherent construction and "hook up" processor and its internal memory. determined what function they would perform. The revolutionary concept of the computer was an idea where a general set of basic THE 1101 COMPUTER operations, which could be called out in any sequence, would operate on "data" provided, The 1101 computer is noteworthy since it was and return and store the results. The "data" the first "1100". It was a commercial offering could be numbers or codes representing letters of a version of the first stored program and words. computer designed by Engineering Research Associates (ERA) under a Navy contract and This programmability of computers, which we delivered in 1950. While this was only a 24- all now take for granted, is really what makes bit machine with no actual commercial sales, them so powerful since it allows them to be it did provide an engineering learning base for 1 the very successful 1103 which followed it. Vacuum Tubes And the old timers like to recall how the Most of the 1103 vacuum tubes were triodes. commercial model number was chosen: 1101 A triode contains a filament which is heated is the binary representation for the number by current passing through it and is placed 13, the task number the Navy assigned to the close to a "cathode" which in turn becomes hot original development contract. causing electrons to be emitted from a rare earth coating on the cathode surface. The negatively charged electrons are attracted to a THE 1103 UNIVAC SCIENTIFIC surrounding positively charged anode or COMPUTER "plate". When a fine mesh termed a "grid" is placed between the cathode and plate, it acts The 1103 was the first 1100 computer with as a control element. A negative voltage on significant commercial sales. It was introduced the grid can greatly reduce the current going in 1953 as the Univac Scientific Computer. It to the plate. Usually about 100 to 200 volts is set the standard for the 1100 36-bit word, applied to the plate, and about -20 volts on the although its internal organization was grid can cut off the tube current. Two triodes changed radically in later machines. Logic were contained in one tube envelope, and this was done with vacuum tubes and crystal pair could make one flip flop. A flip flop, diodes, mounted on many "suitcase" chassis. storing one bit of information could be set to a A total of about 3900 tubes and 9000 diodes "one", cleared to a "zero", or toggled, i.e. , were required. Total power for an installation changed to its opposite state. The later could be up to about 100 kilowatts including function was quite handy in certain logic and that for the air conditioner, chilled water arithmetic operations. Capacitors stored the supply and associated blowers. The state of the flip flop for a short time so it would recommended floor space was at least 58 by 30 not toggle twice ' with a single input pulse. feet for the 38,000 pound computer and its Another triode was usually connected to each supporting equipment. flip flop output as a "cathode follower" (with "its output taken from the cathode rather than the usual plate). This isolated the output wiring load from the flip flop allowing it to change its state faster. The 1103 used about 12 types of tubes; the most common was the 5963 dual triode, an industrial version of the 12AU7, a common part in home tele­ vision sets at the time. The 1103 "suitcase" chassis opened up easily for test and repair. 2 Another tube type that was available then was with lowered filament voltages. This reduced a pentode (so called since it had five rather the tube currents and simulated end of life than the three basic components of the triode). conditions on the weaker tubes so they could The pentode required less control grid voltage be replaced before they failed. Thus "marginal change for a corresponding plate current checking" was born and is still being used even change and has two special grids. In a though most modern parts do not fail often by modified version, the 7 AK7 dual control gradual deterioration. pentode, one of these grids was made to provide an extra control grid. Therefore, a fast One additional new problem was seen in some two-input "AND" circuit could be made since vacuum tubes. If they were held in a cutoff plate current would flow only when both grids condition for a long time, something happened were positive. This provided the basis of the at the cathode surface so that when the grid "gated pulse amplifier", widely used in the became more positive, plate current would not 1103 computer. One of the inputs was usually reach its full, normal value. Tubes were a narrow clock pulse, and the other a wider originally developed for the radio industry and logic level from another output. Diodes were did not operate in this cutoff mode, so the also used to form "AND" and "OR" circuits, but problem had not been seen there. This the pentode tube circuit was preferred for the "sleeping sickness" problem was eventually narrower pulses. A pulse transformer solved by the vacuum tube manufacturer containing one primary and two secondary changing the cathode coating process. windings on a linear ferrite core and potted in a special package was also a key feature of the Magnetism for Memory gated pulse amplifier. The two secondary Magnetism played a strong role in early windings provided the option of either a memory technology and still does for external positive or negative pulse for the output. The storage such as disks and tapes. It seemed a transformer also allowed the output to be at a natural for this since a magnetic surface could different voltage level than the plate, thereby be magnetized in small areas with each region providing the level shifting needed with a representing a one or zero determined by the vacuum tube circuit. (The plate would swing relative positions of the magnetic north and from about +100 to +200 volts, while the next south poles. Furthermore, these regions could grid needed values in the negative range). be quite small, and no power was consumed to maintain their state. So the principles of Vacuum tubes had several known failure magnetic recording, earlier used for audio, modes: the filament could open, surface were applied to digital storage. But the time particles could fall off the cathode and lodge to retrieve the data from a tape was too long between it and the grid; or, there could be a for the computer internal memory, so the gradual loss of plate current, and hence magnetic drum was invented-a cylinder reduced output signal, as the rare earth coated with an iron-oxide surface and rotating material became depleted from the cathode at high speed.