Because of the variability in the architecture it is difficult to be too rigid on the ABI. In any case part of the purpose of this architecture to allow exploration of different ABI's. Within this section, the identifier R_max is used to indicate the highest numbered register in the architecture.

The meanings of the following registers are defined.

Note in particular no frame pointer is defined. It is up to the implementer to decide policy with regard to use of a frame pointer.