General description

The SI-36 calculator was an early hand-held electronic calculator introduced by DEV-TRON in the early 1970s. It featured a compact design typical of calculators from that era and provided basic arithmetic functions and more advanced set of mathematical functions, making it a scientific calculator. Powered by integrated circuits (ICs), it marked a transition from mechanical to electronic calculators. Today, it’s considered a collector’s item among vintage computing enthusiasts.

The DEV-TRON SI-36 calculator was based on a two-chip set of LSI (Large Scale Integration) chips from MOS Technology. Each of the chips is housed in a ceramic package with 28 pins. It’s possible, though unconfirmed, that MOS Technology was the first manufacturer of integrated circuits to pack the logic of a fully functional scientific calculator into just two chips. This chip set was utilized by various calculator manufacturers. MOS Technology’s main customer for calculator chip sets was Commodore, which eventually acquired the company (renaming it Commodore Semiconductor Technology) to produce chips for Commodore calculators.

Internal structure

The DEV-TRON SI-36 calculator consists of two printed circuit boards.
One serves as the calculator’s computation board. Its main circuits are the MCS2525 and MCS2526 from MOS Technology.
The second board is a membrane keyboard and LED display.
Both boards are connected by a special connector to facilitate assembly and any potential repairs.

Video showing the calculation accuracy of the SI-36 calculator.

The DEV-TRON SI-36 calculator featured a full set of instructions typical of calculators of that time.
Its calculation accuracy and speed were not impressive, but they did not significantly differ from the competition.

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