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IME 86/IME 86-S Electronic Calculator

The Old Calculator Web Museum is pleased to have acquired an IME (Industria Macchine Elettroniche, S.p.A.) IME 86-S calculator and associated peripherals for exposition in the museum. Sincere thanks to Serge Devidts for picking up the machine in Germany and arranging for shipment to the museum.

The IME calculators were the brainchild of Italian engineer and inventor, Massimo Rinaldi. Rinaldi was an expert electronics designer, skilled in transistorized digital electronic design, through education in Italy and later work in the field. In the early 1960's, Rinaldi became aware of a desktop electronic calculator built in England called the Anita. This machine used electronic tubes called Thyratrons and Dekatrons to perform math at a much higher speed than motorized mechanical calculators, and it did so silently. Rinaldi believed that he could design a better electronic calculator based on transistorized computer technology what would make for a smaller, faster, and more reliable desktop calculator. He developed his own prototype machine that was used to convince investors that his machine was a major improvement over the British machine. In 1963, Industria Macchine Elettronich, S.p.A. was formed as a subsidiary of the large Italian diversified conglomerate, Edison Group. A shop in Rome, Italy was set up, and work began immediately on turning Rinaldi's prototype into a production quality desktop electronic calculator.

The resulting machine, the IME-84, is stated by IME as being the first solid-state electronic calculator. While the IME-84 was among the earliest transistorized electronic calculators, there are other contenders for the title of first solid-state desktop electornic calculator to market. Along with the IME 84, there were the Friden 130; the Monroe EPIC-2000; the Mathatronics Mathatron, and the Sharp Compet 10. All of these machines came to mass market during 1964. Who was actually first is a battle of definition more than anything else, as some of the machines were introduced in 1963, but weren't actually available for customer shipment until sometime in 1964. There are also some issues about the true definition of solid state. Some of the machines (the Friden 130 and Monroe EPIC 2000, for example) utilized magnetostrictive delay lines as their data storage medium -- a technology which can be argued is more electromechanical than solid-state. The Mathatronics Mathatron was truly a solid-state machine, using magnetic core memory for storage. The Mathatron was shipped to its first paying customer in late 1963, so technically, it predated the IME 84 to market.

The early IME calculators were masterpieces of design; electronically, mechanically, and aestheticaly. Electronically, the machines used computer engineering concepts in the logic design, making the machines similar in architecture to small computers. Some of the other early calculators used architectures similar to their mechanical predecessors, with circuitry that counted by tens instead of using binary arithmetic; and utilized control methods that were essentially electronic emulations of the cams, gears, and linkages that made mechanical calculators operate. The logic of IME's machines was designed to be extensible, providing the potential for addition of peripheral devices. Mechanically, the machines were packaged such that they were modular, making for ease of service. Despite the modular design, great efficiency in space utilization was part of the design, to make the machines significantly smaller than that of competitors, while still providin sufficient cooling through convection to avoid the need for a noisy fan. Stylistically, the machines were sleek, with a very modern look that made them the technology centerpiece in any setting. From an operational standpoint, the early IME calculators could be a bit daunting to use for someone who was not familiar with their operation. The machines use a three-register architecture, with an input register, an accumulator register, and a counter register, similar to the three register architecture of later design electromechanical calculators. The user had to select the proper register for inputting numbers into the machine, and also to display the correct register containing the result of calculations. Other calculators from the period were easier to use, with a stack architecture (Friden, Monroe), pure alegbraic logic (Mathatronics), or a simple arithmetic architecture (Hayakawa/Sharp).

The IME-86 was a follow-on to the design of the IME-84, designed to provide even more expandability than its predecessor, as well as making improvements to make the machine easier to use. It is based on the same basic design concept as the IME 84, but with greater numeric capacity, and the addition of an (optional) single-key square root function. There was also the IME 86-S model, which added the capability to interface to a diverse range of peripherals. With its peripheral capabilities, the IME 86-S could become the centerpiece of a true computing system that could rival small computer systems of the time, at a much less expensive pricetag.

An IME KB-6 Remote Keyboard/Display Unit

The IME-86-S calculator was designed to be the centerpiece of a multi-component calculating system. The machine was designed with expansion capabilities in mind. A fairly wide range of options were available for the machine, including remote keyboard/display units (Model KB-6) which could connect to the main calculator through a "hub" that allows up to sixteen remote keyboard/display units to be connected, although only one unit at a time can access the calculator (unlike the Wang 300-series "SE"-model calculators, which could serve four simultaneous users). Also available were an external printer, keyboard-only units, external core memory expansion units (MS-306), and programmer units, including the Model DG-308 and DG-408 "Digicorder" devices that transform the IME 86 into a learn-mode programmable calculator. The Digicorder programmers also provide a built-in punched card reader, which allowed read-in of programs from specially coded punched cards. . Along with the desktop calculator form-factor, IME also produced rackmount versions of the calculating engine (IME 86-S RM) and peripherals that would allow a complete calculating "mainframe" to be created.

The IME Model DG-308 Digicorder
Image Courtesy Serge Devidts

The IME 86 is an all-transistor (mostly Germanium PNP) machine, with Nixie tube display. Magnetic core memory provides working memory register storage. The machine carries out the basic four math functions along with an optional automatic square root (which uses memory register four as a scratch register during the calculation). The square root function logic was built into the machine, with the cost of the square root option simply being that of providing a new keyboard bezel, and a keycap for the already-present square root keyswitch. Four accumulator-style memory registers are provided, making the machine particularly useful for more complex operations involving multiple intermediate results. With a capacity of 16 digits, the machine provides plenty of capacity for financial or scientific calculating. The 86 is a fixed-decimal point machine, with two keys [.->] and [<-.] which are used to set the decimal point position at any position.