The Commodore 886D calculator, introduced in 1974, is a notable entry in the history of electronic calculators. Manufactured by Commodore in the United States, this device exemplifies the technological advancements of its time, despite certain idiosyncrasies in its design and functionality.
The calculator measures 77.2mm by 146.4mm by 24.3mm (width, height, depth), making it compact and portable. It weighs 118 grams without batteries, contributing to its ease of use. The power supply consists of a 9V DC PP3 size battery, with an option for an adaptor (DC-620R or 505) through a socket located on the top side. Notably, the batteries must be removed before using an adaptor to avoid potential damage.
The Commodore 886D features a two-piece matte plastic case in a light cream color. The top area prominently displays a raised and printed black and silver Commodore logo within its own recess. The red plastic filter is heavily tilted and inset, accompanied by a black painted panel underneath. The keyboard surround, made of matte black plastic, has raised areas for each key, adhering to Commodore’s typical key color scheme. The large, squishy keys are responsive, and the display is highly magnified and clear, albeit with a limited viewing angle.
The display is an 8-digit red LED with a bubble lens, including a ninth digit for negative and error indication. The calculator offers standard four functions, percentages, and register exchange, catering to basic arithmetic needs.
Logic
- The (C) button is used once to cancel the last number entered and a second time to clear the whole calculator, effectively functioning as a C/CE button.
- Automatic constant is available on all four functions.
- Input overflow is suppressed; inputting a ninth digit is ignored.
- Negative numbers are shown with a “-” in the immediate left-hand digit, traveling into the far left (ninth) to allow eight-digit negative numbers.
- Divide by zero shows “E00000000” (no decimal point) and is recoverable by dividing by one.
- Overflow shows the result with “E” (negative or positive) in the leftmost (ninth) digit and is recoverable by continual division by 10 (or a multiple). The maximum number you can recover from is x1048, as you can carry on using the overflow number.
- The (EX) button is used to exchange the display with the register.
- The (%) button divides by 100 and can also be used to recover from overflows.
- It suffers from the negative zero bug: (0)(-)(1)(=) gives “-1,” then (+)(1)(=) will give “-0.”
- It suffers from the divide to negative zero bug: (0)(-)(1)(=) gives “-1,” then (/)(1)(0)(=)(=)(=)… etc., will eventually result in “-0.”
Summary
The Commodore 886D calculator, despite its early age, features a minimalistic component design. It includes a Commodore RBP-01-B (or 8) 7449 CPU, a National Semiconductor 512 DS8855N display driver, a 9-digit single unit Optostic bubble lens LED display, and a capacitor. The main CPU board sits loose above the keyboard assembly and is connected by a 14-way ribbon cable. The calculator’s logic, while functional, has several quirks and bugs, such as the ability to recover from overflow and divide by zero errors, and the presence of negative zero bugs. Despite these peculiarities, the Commodore 886D remains a fascinating artifact of early calculator technology.
