There is no ALU chip. Or rather, there is; it’s just that an entire RISC CPU is implemented in basic logic chips and a whole lot of microcode on the ROM. It’s weird, yes, but it is cool.

The result is a simple yet fully functional 64-bit CPU with 32 registers, 32kB main memory and a separate 16kB stack. The instruction set mostly contains ALU and branching operations, but also a ...