An
instruction set where all (or most)
instructions have the same format and all registers and
addressing modes can be used interchangeably - the choices
of
op code, register, and addressing mode are mutually
independent (loosely speaking, the choices are
"
orthogonal"). This contrasts with some early
Intel
microprocessors where only certain registers could be used
by certain instructions.
Examples include the
PDP-11,
680x0,
ARM,
VAX.