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Cat Machine is a project that defines a 32bit CPU architecture, implements it in a VM, and implements an assembler for a custom assembly language. The inspiration behind this project is old consoles, the idea is that you can write a game or application using our ASM and then run it with a limited CPU clock rate to simulate poor hardware, this means that you can focus on optimisation knowing that it will mean something.
- Registers – the encodable and non-encodable register file, plus the flags layout.
- Instructions – every opcode, its operand encoding, cycle cost and privilege requirement.
- Memory – memory layout at boot, the stack, bounds checking and the ROM/reset behaviour.
- Virtual Mode – the user/kernel privilege model, address translation, and the interrupt frame format.
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Interrupts – the standard interrupt numbers, the handler-table format and
iret. - Serial Protocol – how the VM talks to virtual peripherals.
- Display – display modes, palettes, tiles and sprites.
- Assembly – syntax for the Cat assembler, including macros, includes and debug symbols.
- Catnip Programming – the higher-level Catnip language that compiles down to Cat assembly.
The VM allows configuring the CPU cycles per second, the available memory, and the available debugging tools. You pass the VM a ROM file, which is then loaded into memory and execution begins at address 0.
The assembler supports most modern assembler features like assemble-time constants and expressions, #include, macros, reserving and defining raw data, including raw data files, etc. Every assembled ROM is paired with a JSON debug-symbol file so debuggers and other tooling can show source lines and symbolic addresses.