CPU Performance

Clock cycle

One basic timing interval of a processor.

Clock rate

Number of CPU clock cycles occurring per second, usually measured in hertz.

Hertz

One cycle per second.

Gigahertz (GHz)

One billion cycles per second.

Clock cycle time

Amount of time required for one CPU clock cycle.

Instruction count

Total number of instructions executed by a program.

CPI

Cycles Per Instruction; average number of clock cycles required per instruction.

CPU execution time

Time the CPU spends executing a program.

CPU time formula

CPU time = Instruction count × CPI × Clock cycle time.

CPU time using clock rate

CPU time = (Instruction count × CPI) / Clock rate.

Performance

How quickly a computer completes a task.

Amdahl's Law

Shows that overall performance improvement is limited by the portion of a system that cannot be improve