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Sharp QT-8D "micro Compet"

Sharp QT-8D

Sharp QT-8D with stylised "Itron" vacuum fluorescent display, with half-height zero, showing 12345670.

Sharp QT-8D "micro Compet"

Display is 8 digits, green vacuum fluorescent "Itron" tubes.

4 functions.

"Has four MOS/LSI chips and a clock generator. Each chip contains 900 MOS transistor equivalents." (Electronic Design, Jan. 1971).
"The logic tasks are split up among the four packages. The first, called the NRD 2256, handles the display and numerical read-in functions. Decimal-point control is taken care of by the second circuit, the DC 2266. The third, AU 2276, handles digital addition and register input control. The fourth the AC 2266, rides herd on the arithmetic and provides the registers." (Electronics, March 1969).

See below for further information on the development of this model.

245 x 132 x 70 mm. (9.6" x 5.2" x 2.75").

Advertised October 1969.

Made in Japan.

Price, in UK. in 1971, £199 Sterling (about US$475).

By replacing the power supply circuitry with rechargeable cells Sharp produced the QT-8B, the first battery-powered electronic calculator.


The Itron VFD display tubes. One of the reasons for having a display with half-height zeros is that there is no leading-zero suppression. The half-height zeros then make the display more easily readable.

Inside Sharp QT-8D

The calculator opened. On the left are the display board and the calculating board, which both plug into a two-slot socket.

LSI integrated circuits

With the display board unplugged showing the whole of the calculating board with the four Rockwell Large-Scale Integration (LSI) integrated circuits. The clock-generator integrated circuit has a star-shaped heat-sink clipped on.

Sharp Corporation has kindly provided information upon which the following is based:

By mid 1960's US manufacturers had opened a new page in semiconductor technology, i.e. LSI (Large-Scale Integration) ICs based on MOS (Metal-Oxide Semiconductor) technology. This made it possible to integrate thousands of transistors on a single chip.
Although the U.S. semiconductor manufacturer Texas Instruments (TI) first demonstrated a prototype electronic calculator, called the "Cal-Tech", using this technology in late 1966, the comapny was not ready to move into the consumer electronics market, remaining a component manufacturer.
Besides TI, there were several LSI manufacturers, such as Motorola, AMI, Fairchild Semiconductor, RCA, National Semiconductor, and Rockwell (North American Rockwell), to which Dr. Tadashi Sasaki of Sharp attempted to offer the collaboration on developing a LSI calculator. However, it was only Rockwell's Autonetics Division that accepted the offer of Dr. Sasaki, and a business agreement between these two companies was soon reached. 

A team of system design engineers, headed by Yukihiro Yoshida, was sent to Rockwell where, with the support of Rockwell's design capability, they set about implementing the required set of MOS-LSI circuits by using the four-phase MOS dynamic logic which was originally developed by Rockwell. After a few years of hard work the design team succeeded in developing a LSI calculator, the Sharp Compet QT-8D, based on just four MOS-LSI chips produced by Rockwell. This was manufactured in the Nara factory, in Japan, and put on the market in August of 1969. This time there was a drastic reduction in price to 98,000 yen (US$270), weight to 1.4Kg (  pounds), and power consumption to 4W (using 4 MOS-LSI's and an 8-digit display using VFD tubes).


For further information about Sharp Corporation and its calculators visit the Calculator Companies section of this site.

Addo-X 9354J

Addo-X 9354J, a version of the Sharp QT-8D made for sale by Addo, by then owned by Electrolux of Sweden.

Sharp were pioneers in the field of calculator electronics and had a collaboration agreement with Rockwell to develop Large-Scale Integration (LSI) integrated circuits for calculators, thereby greatly reducing the component count. They were first used in the AC powered QT-8D of late 1968 which used just 4 LSI ics, 1 MSI ic, and 1 SSI ic.

An advertisment in the journal "Electronics" of September 1970 proclaimed "North American Rockwell became the world's largest producer of advanced MOS/LSI circuits when the Sharp Corporation of Japan signed a $30-million contract for these components.
Sharp now makes more than 30,000 of these calculators a month. Since the initial contract Sharp has signed an even larger follow-on contract.

The 8-digit display and floating point helped reduce the width of the calculator.
Most of the contemporary calculators using MSI integrated circuits had fixed decimal points and so required many digits in the display.
By using a floating decimal point this calculator could get away with 8 digits and so reduce the width.

The small size of the QT-8D allowed the development of a hand-holdable version using batteries, the QT-8B - the first battery-powered electronic calculator.

Sharp Compet 22, Sharp QT-8D, Sharp EL-801

From left to right, Sharp Compet 22, Sharp QT-8D, Sharp EL-801.

Sharp Compet 22, Sharp QT-8D, Sharp EL-801

The photographs above and on the left illustrate the size reduction over about 4 years made possible by developments in integrated circuits.

On the left, from top to bottom:

  • Sharp Compet 22 of 1968, with many medium-scale integration (MSI) integrated circuits, AC powered.
  • Sharp QT-8D of 1969, with four large-scale integration (LSI) integrated circuits, AC powered.
  • Sharp EL-801 of 1972, with two CMOS LSI integrated circuits, battery powered.

Vintage Calculators

© Text & photographs copyright Nigel Tout   2000-2017  except where noted otherwise.