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
||Canon Camera Co., Inc.
||$2,395 at Introduction
||$2,150 (August, 1968)
||Canon-made electro-optical display elements
||Incandescent lamp edge-lighting of plastic panels etched w/numerals
||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
||Automatic floating decimal point
||Four Function w/Automatic Square & Square Root
||Seven. Five Store/Recall, Two Accumulating, all with 16-digit capacity and floating decimal point
||Addition/Subtraction: 10mS; Multiplication: 900mS; Division: 1 sec.; Square Root: 600mS; Square: 400mS
||17" wide, 23 1/2" deep, 8 1/2" high
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