As an instruction set architecture, a particular ISA generally defines a platform of cross-compatible microprocessors. PowerPC, x86, ARM, 680x0, and 6800 are some of the most popular ISAs today.

An ISA cannot be deemed RISC or CISC by the number of instructions it has. To count instructions, one normally looks at a list of assembly language mnemonics. However, the assignment of names to opcodes is arbitrary. One can always reduce the number of mnemonics by reassigning opcode bits to be parameters, or by having lots of complex operand forms and addressing modes a la 680x0 assembly language.

The definition of RISC is subjective and open to opinion, but thorough analyses of the ISA and the microarchitectures that use it are necessary before applying any label.