Chip multiprocessors — also called multi-core microprocessors or CMPs for short — are
now the only way to build high-performance microprocessors, for a variety of reasons. Large
uniprocessors are no longer scaling in performance, because it is only possible to extract a
limited amount of parallelism from a typical instruction stream using conventional superscalar
instruction issue techniques. In addition, one cannot simply ratchet up the clock speed on
today’s processors, or the power dissipation will become prohibitive in all but water-cooled
systems. Compounding these problems is the simple fact that with the immense numbers
of transistors available on today’s microprocessor chips, it is too costly to design and debug
ever-larger processors every year or two.
