Home > Articles > Hardware

Superscalar Execution

The fifth-generation Pentium and newer processors feature multiple internal instruction execution pipelines, which enable them to execute multiple instructions at the same time. The 486 and all preceding chips can perform only a single instruction at a time. Intel calls the capability to execute more than one instruction at a time superscalar technology. This technology provides additional performance compared with the 486.

See "Pentium Processor."

Superscalar architecture usually is associated with high-output RISC (Reduced Instruction Set Computer) chips. An RISC chip has a less complicated instruction set with fewer and simpler instructions. Although each instruction accomplishes less, overall the clock speed can be higher, which can usually increase performance. The Pentium is one of the first CISC (Complex Instruction Set Computer) chips to be considered superscalar. A CISC chip uses a richer, fuller- featured instruction set, which has more complicated instructions. As an example, say you wanted to instruct a robot to screw in a light bulb. Using CISC instructions you would say

  1. Pick up the bulb.

  2. Insert it into the socket.

  3. Rotate clockwise until tight.

Using RISC instructions you would say something more along the lines of

  1. Lower hand.

  2. Grasp bulb.

  3. Raise hand.

  4. Insert bulb into socket.

  5. Rotate clockwise one turn.

  6. Is bulb tight? If not repeat step 5.

  7. End.

Overall many more RISC instructions are required to do the job because each instruction is simpler (reduced) and does less. The advantage is that there are fewer overall commands the robot (or processor) has to deal with, and it can execute the individual commands more quickly, and thus in many cases execute the complete task (or program) more quickly as well. The debate goes on whether RISC or CISC is really better, but in reality there is no such thing as a pure RISC or CISC chip, it is all just a matter of definition, and the lines are somewhat arbitrary.

Intel and compatible processors have generally been regarded as CISC chips, although the fifth- and sixth-generation versions have many RISC attributes and internally break CISC instructions down into RISC versions.

  • + Share This
  • 🔖 Save To Your Account

Related Resources

There are currently no related titles. Please check back later.