(ISA) The parts of a
processor's design that
need to be understood in order to write
assembly language,
such as the
machine language instructions and registers.
Parts of the architecture that are left to the implementation,
such as number of
superscalar functional units,
cache
size and
cycle speed, are not part of the ISA.
The definition of
SPARC, for example, carefully
distinguishes between an implementation and a specification.