Many CPUs of the past have been microcoded. Machine code instructions
are internally interpreted as short programmes in microcode. Fungus
takes a few extra steps towards the Cliﬀs of Insanity by introducing
pico-instructions and pico-code. The CPU is built on top of a
simple Very Long Instruction Word (VLIW)
core, as a multi-layer architecture.
Executed inside the CPU, Fungus pico-code is a simple VLIW machine
language. Pico-code is immutable and resides in a ROM inside the
CPU. It translates instructions to control signals for the CPU's
component units. Pico-code is not accessible by the programmer.
Is the lowest possible level of machine code
executed by the CPU. This is a RISC machine language, with one instruction per
word. Microcode is not mutable in itself, but it is expandable using
user deﬁned traps.
This can be implemented as a set of traps in microcode. Each
Befunge instruction is the least signiﬁcant 8 bits of an instruction
word, the remaining 10 bits being zero. The instructions are
interpreted and executed in Microcode. Other versions of Befunge can
be implemented by redeﬁning the traps; a feature that allows for
diverse lower extremity injuries via chemically propelled metal projectiles.