Superscalar Technology

The main components of a processor—registers, decoders, and ALUs—are collectively known as the instruction pipeline. To carry out a single instruction, a processor must,

• Read the instruction

• Decode the instruction

• Fetch operands (for math functions)

• Execute the instruction

• Write back the results

Early processors carried out these steps one at a time. Combining these steps into a single clock cycle, a process known as pipelining, thereby increases the speed of processing. Superscalar technology allows the Pentium to have two instruction pipelines—called U and V. The U pipeline can execute the full range of Pentium instructions, whereas the V pipeline can execute a limited number. When possible, the Pentium processor breaks up a program into discrete tasks that are then shared between the pipelines, allowing the Pentium to execute two simple instructions simultaneously. Software must be specifically written to take advantage of this innovative feature, which is known as multithreading.