Advanced Personal Computer (PC) Concepts

After the initial years of the PC (let's say 1980-1986), the search for more efficient PCs, capable of greater processing power, speed, and felexibility went into high gear.

SUPERSCALAR:

The term "superscalar" was coined before 1964, when the first 'superscalar' processor (a CDC 6600) was introduced. Several premises were made as follows:

  1. Program steps are often listed sequentially; but they don't always have to be executed in the exact sequence they are listed.
  2. The ability to "issue" more than one instruction per clock cycle.
  3. The superscalar computer can issue a small number of instructions (2 to 4) per clock cycle.
  4. The instructions must be independent.
  5. The concept can be used on both CISC and RISC computers.
  6. Superscalar capability means that the system can execute independent units of instructions at the same time others are executing.
  7. It attempts to "predict" branches in programs, and starts executing the predicted branch. Some manufacturers claim up to 80% accuracy in predicting branches.

So, a superscalar processor provides "two or more execution paths" for programs, so it can process two or more program parts simultaneously.

Superscalar goes beyond the speed gained by using shorter micron circuitry, although this helps. Superscalar architecture introduces more complexity into its circuitry.

Most of the newer microprocessors, and especially the multi-cpu machines will almost have a 'superscalar' capability in their design. An Intel Pentium, for example, has two parallel pipelined execution paths.

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