Pesky Moose & Squirrel

CPU8 Hints & Support

Source Programming Hints:

  1. In Assemble, use the bottom left File icon to open the source directory. There are 6 example source files there.
  2. You can change and modify each of the example source files as you wish. Remember to Save it you want to keep.
  3. You can add your own source programs. Clear the edit field -- use File icon and select the + symbol top right.
  4. Assemble source using the Assemble button top right.
  5. After assemble, use the Save button, bottom left, to save the assembled object code for future execution.
  6. In the source edit field, use the Tab key (iPad Pro models only) to align fields. (Or double tap Space Bar for tab.)
  7. The Assembler Manual is found via the Book icon on the bottom right of edit field.

Running Program Hints:

  1. Like a real computer, you must first power it on to use it. This will display an Overview of the Architecture.
  2. The IPL button will load the computer microcode. These define the hardware instructions and are listed for view.
  3. The Load button will display the object directory. If it is empty, you must first assemble a program and save object.
  4. The Loaded program will be displayed via a memory and register dump.
  5. The Run button will start the clock and display the microcode progress via display lights and LED output.
  6. The Step button will step through the instructions and wait for you to continue -- displaying status on each step.
  7. The Halt button will stop the clock and the end of the current instruction (it will complete instruction microcode steps).
  8. Once halted, the program may be continued via the Run button.
  9. Display and clock speed options can be controlled via the Settings main screen menu.

Settings Hints:

  1. You can decide to show or hide the register & program dumps after each microcode step and/or each instruction.
  2. To help visualize real computer start up, you can decide to fill registers and memory with initial values that are:
    • Random -- like you'd find with a real computer at start up
    • Predicable contents -- zeros in registers and memory address in memory each location
  3. You can set the frequency of the clock, in seconds. Slow the clock to see more detail or speed it up to get results.
  4. At certain clock speeds, the register and memory dumps become unusable and are therefore turned off automatically.
  5. The slider will equate the clock timing from seconds to hertz so you can compare CPU speeds to other computers.

Video Hints:

  1. The videos are provided to give the user an indepth understanding of all aspects to the CPU8 model.
  2. While describing the details about each CPU, Ben Eater provides an astonishing treasure trove of information.

What Else?

If you run into problems, have suggestions or would like to contribute to this project, please send an email to: and we will respond as soon as we can.

Enjoy and let us know if you write an interesting new program.

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