This page aims to provide a rough guide on how to port RISC OS to new hardware.
RISC OS can be built to target various different “machine types”. In the past the machine type has been used to target specific computers (e.g. RiscPC, Iyonix, different STB models), but now it’s generally used to refer to the different CPU architecture(s) that must be supported. So if you’ve added a new CPU to the list of known CPUs in the kernel, you may need to add a new machine type to go with it. Specifically, if it’s using a different CPU (sub) architecture, then adding a new machine type will allow the compilers to generate code which is compatible with the CPU, or takes advantages of new instructions. Or if the CPU requires a new MMU interface file to be added to the kernel (or needs other kernel changes that can’t realistically be accounted for at runtime) then adding a new machine type is the way to deal with that.
There are several places where the machine types are set up: