February, 2020:

I was particularly impressed with the way the Wang 360 worked - especially the way it multiplies and divides using logarithms instead of repeated addition.

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I wanted to build a similar calculator 'from scratch' - using logic chips only (no calculator chips allowed).

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September, 2020:

Settled on a design:

• Interface:

  • 8-digit display​

    • positive integers only​

  • 0-9 keyboard

  • two internal 8-digit registers

    • "accumulator" for addition and subtraction​

    • "log accumulator" for multiplication and division

  • function keys:

    • "+" add to accumulator and display result​

    • "-" subtract from accumulator and display results

    • "x" multiply into log accumulator (add log of display to log accumulator)

    • "÷" divide into log accumulator (subtract log of display from log accumulator)

    • "Clr" clear the accumulator

    • "Disp" show the anti-log of the log accumulator (clears log accumulator)

• Hardware:

  • based on AM2901 ALU and AM2910 sequence controller

  • microcode ROM modeled with Teensy 3.2 (it's easier to re-program than EPROMS)

  • the remainder are 74LSxx TTL chips

  • mixture of custom PC board and wire-wrap

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June 2021:

Finally all assembled and working:

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