Magic-1 computer on Logisim

Simulate Bill Buzbee's Magic-1 computer with Logisim Evolution

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The Magic-1 computer from Bill Buzbee can be simulated with Logisim Evolution.

This project is a good exercise for learning Logisim Evolution and evaluating its capacities.

It's very easy to use, it's quite capable and delivers when I ask a lot.

The Magic-1 computer from Bill Buzbee is an excellent candidate for evaluating Logisim and see if it can simulate a homemade computer.

Note: use the logi7400ic.circ file from my github project, not the original one (link provided) since it won't work with the current version of logisim.

  • Last correction

    Jacques Pelletier07/10/2021 at 09:08 0 comments

    I inverted the latch outputs entering U47 in Faults & Interrupts.

    This corrected a bug where the CPU was doing an NP fault right after reset.

    With this, the fibonaci test seems to run fine (no way to check).

    This will be the last modif for a while unless someone finds a bug.

    All the code is on github on the link provided.

    Time to go on other projects!

  • 'Call' and 'return' now working for real

    Jacques Pelletier07/02/2021 at 04:34 0 comments

    The original microcode was OK. There was some errors in the field decode. Polarity of CLKS and U43D was wrong.

  • False alarm, call not working

    Jacques Pelletier06/29/2021 at 07:50 0 comments

    Call just immediately return instead of executing the subroutine.

  • Call debugged

    Jacques Pelletier06/28/2021 at 01:14 0 comments

    I had to tweak the microcode to make call work. The original microcode was adding 2 times the displacement, thus messing the return address. It's probably due to my implementation of the clock circuit with a state machine instead of a few delays.

    So now, call and return work.

  • Fibonaci test

    Jacques Pelletier06/22/2021 at 07:36 0 comments

    I'm currently testing the Fibonaci test. The code has been provided by Mr. Buzbee.

    It's not yet confirmed to work, it seems to end prematurely with a halt.

  • It's alive!

    Jacques Pelletier06/20/2021 at 12:51 0 comments

    Now, stepping works with NOPs. It's alive!

  • Not yet stepping

    Jacques Pelletier06/19/2021 at 10:36 0 comments

    Added the original microcode from Buzbee's own files.

    Added bus swappers on RAM and ROM memories to match the circuit.

    Solved some bus conflicts.

    With the ROM filled with NOPs; so far, it gets the first op from the ROM, but the bus address doesn't increment.

  • Running with microcode

    Jacques Pelletier06/14/2021 at 04:52 0 comments

    The microcode seems to be running, not sure what it's doing yet.

  • Microcode generator done

    Jacques Pelletier06/13/2021 at 17:57 0 comments

    I modified Buzbee's code to generate the microcode from C instead of using scripts.

    Some minor corrections to Logisim files.

  • Batch of fixup done!

    Jacques Pelletier06/12/2021 at 06:21 0 comments


    The logic74xxic needed some rework to upgrade to Logisim Ev. 3.4.1:

    5-input gates corrected in all circuits

    Flip-flops corrected, all chip corrected


    The higher schematics were cleaned a lot, upgraded all the chips

    Clock module is implemented with buffer instead of delays.

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