IME 84 Calculator Technology

The IME 84 was implemented with probably the best technology choices of its day

All solid-state, Germanium transistors were the standard technology of the day despite being temperature sensitive. It’s interesting to see that the design specifically provides power supply ventilation through the slots at the top of the keyboard, preventing heat from entering the logic card cage.
Core memory was relatively new in the early 1960s but its advantages of fast random access and easy expansion made it a better choice than delay lines
Nixie display was cheaper and simpler than a CRT, these advantages would become more significant as calculator prices were driven down.
Expansion and Interfacing would become a significant point of difference. Wang was the only other manufacturer to pursue this facility and their design was never so well integrated.

The industrial design and construction of the IME 84 was also of a superior standard. The external design is smooth, low and sleek - it still has a modern look that seems to say “Italian Style” even 50+ years later.

The internal construction is equally well-thought out and highly designed. The folding card cage presents a clean look and keeps the card connections close together with short interconnects.

It is interesting to note that at least half of the transistors are marked “RAY”, suggesting that they were made by Raytheon. Raytheon was largely out of the transistor manufacturing business by the first years of the 1960s but IME seems to have had a very large supply of RAY branded transistors. The rest of the transistors are by COSEM or TI. COSEM was a French based company that did not transition into IC manufacture while TI obviously went on to become a leading microelectronics company.

IME 84 Hardware Patch

The IME 84 has been said to have a very complete and correct implementation, but this unit is also found to have a hardware patch. Some other DoPECC machines have simpler modifications with PCB traces cut and links added, this is the only machine that has an added board with a circuit of some complexity.

There are four COSEM (French) transistors and six diodes mounted on Veroboard (a British brand), which suggests this was done by the British agent after delivery. It’s not immediately clear if this is a patch for a design defect or a field modification to alter or extend functionality.