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Canon Canola 167 Desktop Calculator

Canon Canola 167

The Canon Canola 167 is a rather unique electronic calculator, as it utilizes a small magnetic drum for its main register storage. The Canola 167 is the only desktop electronic calculator known to have been marketed that used this type of memory technology. The only other known electronic calculator to use a magnetic rotating memory was Wyle Laboratories' Model WS-01 calcualtor, which used in essence and inside-out rotating magnetic drum for its storage element. Other electronic calculators of the era utilize recirculating magnetostrictive delay lines, chains of transistorized or IC-based shift registers/ring counters, magnetic core memory, or in the case of Toshiba's early electronic calculators, charges stored in capacitors, as the storage element in the machines. The fact that the Canola 167 uses a magnetic drum is reflected in the somewhat slow calculation times quoted for the calculator. Division operations are quoted by Canon as taking up to one second. In order for calculations to be performed, the electronics must wait for the bits of the digits it is working on to rotate into place for a magnetic read/write head to be able to read the data. To write the result of a calculation back into storage the electronics must again wait for the drum to rotate to the correct position to write the result. The speed of the physical rotation of the drum determined the operational speed of the calculator. In fact, that master timing for the calculator is generated by special read-only clock track(s) on the drum.

The magnetic drum memory device in the Canon Canola 167 was manufactured for Canon by Mitsubishi Electric. Mitsubishi had developed its magnetic drum data storage technology for its MELCOM series of electronic computers beginning in the early 1960's, and in time developed the technology to the point where the company produced small magnetic drum memory units either to customer specifications, or in standardized forms, for sale to customers. The small Mitsubishi Electric drum memory used in the Canola 167 calculator is an example of this aspect of Mitsubishi's storage system business. Later, Mitsubushi did the same thing with Magnetic Core memory, shrinking it down from the large core memory arrays used in their computer systems, to much smaller core arrays that were sold to customers for use in devices such as electronic calculators, cash registers, accounting machines, and other small-scale systems that required modest amounts of storage. Mitsubishi manufactured small core memory arrays that were used by quite a number of electronic calculator manufacturers, among them, Casio, Hayakawa Electric (Sharp), and Nippon Calculating Machine Co. (Busicom).


The Mitsubishi-manufactured magnetic drum memory unit in the Canon Canola 167
The drum enclosure is at the bottom with six heads connected with small coaxial cables.
The drive motor is above the drum, with a belt connecting the two in the semi-transparent plastic shield on the left
Image Courtesy of Serge Devidts, Calcuseum

The magnetic drum measures 1.2 inches in diameter and is just under 2 inches wide. It was reported to rotate at a speedy 9,300 RPM, a speed necessary to minimize the time the electronics had to wait for the information needed to rotate into position to be written or read. The stated capacity of the drum was approximately 3,000 bits, although that is likely a statement of the raw capacity of the drum, and not the actual number of bits that were required to store the registers of the calculator. The drum contained eleven registers of sixteen digits each, plus likely an additional digit that kept track of the decimal point location within each register. If the calculator represented digits in the registers in a 4-bit fashion (e.g., Binary-Coded Decimal), this would account for only 748 bits. If the calculator used a pulse-counting representation (e.g., a timeslot with zero through nine pulses representing each digit), that would account for somewhere around 1,870 bits, still rather shy of the stated 3,000 bits. It is possible that some other means of representing the digits of the registers was used, or there was some overhead for perhaps doing error checking, both of which would require additional data to be stored on the drum.

The Canola 167 was not a hot seller. First off, it was expensive, selling for $2,395 at introduction. The machine also required a period of time when powered up for the drum to get up to speed. The 167 was also rather slow compared to other calculators of the time. The machine also had to be treated with a higher degree of care than other solid-state calculators of the time, as the magnetic drum was sensitive to mechanical shock. Too much of a jolt, especially when powered on, and the read/write heads could crash into the thin magnetic surface of the drum, damaging the drum and rendering the machine inoperative. The only option at that point would be an expensive replacement of the drum. Along with having to exercise great caution when moving the calculator (only after allowing time for the drum to spin down after powering the calculator off) there was also exercise involved in moving the machine around, as the machine weighed just over 50 pounds. The only benefit the 167 had over other calculators on the market at the time was that it had five store/recall memory registers, and two accumulator-type memory registers for storing constants and intermediate results. This memory capacity was overkill for most use cases, especially given the rather high pricetag of the machine. The added cost simply didn't justify a few extra storage registers when compared to other transistorized desktop calculators of the time that sold for considerably less and performed better. Canon quickly abandoned the use of rotating magnetic memory in its calculators, replacing the drum memory of the 167 with magnetostrictive delay lines beginning with its first integrated circuit-based calculator.
Canon Canola 167 Specifications

Manufacturer: Canon Camera Co., Inc.
Model Number: Canola 167
Introduction: Summer, 1967
Manufactured In: Japan
Price: $2,395 at Introduction
$2,150 (August, 1968)
Display Technology: Canon-made electro-optical display elements
Incandescent lamp edge-lighting of plastic panels etched w/numerals
Logic Technology: Discrete Diode-Transistor Logic
Small Mutsubishi-made magnetic drum (11 tracks) for working register storage
Digits of Capacity: 15, w/Double-Precision multiplication mode for 30-digit results
Decimal Modes: Automatic floating decimal point
Math Functions: Four Function w/Automatic Square & Square Root
Memories: Seven. Five Store/Recall, Two Accumulating, all with 16-digit capacity and floating decimal point
Performance: Addition/Subtraction: 10mS; Multiplication: 900mS; Division: 1 sec.; Square Root: 600mS; Square: 400mS
Size: 17" wide, 23 1/2" deep, 8 1/2" high
Weight: 51 pounds
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