EEVblog #663 – Compucorp 322G Calculator Teardown

Teardown Tuesday
Inside a 1973 vintage programmable scientific desktop calculator.
The P2102 is a 1K x 1 bit SRAM, so looks like a 4 bit processor architecture.

Teardown photos:

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  1. My first computer, a 2650 based unit, had 11K of RAM, using 88 x 2102 chips.
    The RAM was on daughter boards of 1K each, stacked on an S100 card.
    I haven’t seen 2102 chips for quite a while. Not long after I started
    playing with the 2650 board, the 6116 2Kx8 chips came out and I remember
    being very impressed. My, how things have changed!

  2. Is it possible that the lack of battery internal resistance is causing the malfunction with the display?

  3. If it is true old school PMOS like the list suggests, that will explain why the power supply scheme looks so complex … these definitely needed more than one power rail, and at odd voltages (-27V,-13V,GND seemed to be common) … now you still need a 5V supply for the TTL and depletion-NMOS (the P2102 is) parts, and all the voltages the plasma display and the drivers need…

    Also, the whole thing seems full of carbon composition(!) resistors with all the problems they can develop… looks anachronistic even for early 70s…

  4. What is the LSI famous for? I couldn’t find much info on it, but you describe as if it were pretty common. Thanks!

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