IBIS is a Custom ISA which is implemented in this datapack.
Currently there is no documentation, but you can create a CPU using these commands:
function ibis:create_cpu(the return value is the id)function ibis:switch_context {cpu_id:<id>}- optionally
/data modify storage ibis:mem_<id> roms set value [{base:0x0000,bytes:[B;...]}](replace...with bytes to execute) function ibis:emu/reset
now you have to manually step the cpu using function ibis:emu/step, because the management of which CPUs are running is up to some other datapack.
This datapack also contains no input/output support (although the CPU does have those instructions, which are implemented when the peripherals addon is installed)