How To Determine a Processor's Speed (MIPS)...

The number of machine code instructions a computer can process while executing a "standard" program is measured in MIPS (Million Instructions Per Second). Specifically, MIPS is a method of measuring the raw speed of a computer's processor and is defined as the number of machine instructions (in millions) that a processor can execute in one second.

                  Processor Clock Frequency (MCLK)             cycles / second      million instructions
   MIPS = ------------------------------------------------ = -------------------- = --------------------
          Average Cycles per Instruction (CPI) * 1,000,000   cycles / instruction          second

MIPS is only an approximation as to a processors performance because some processor instructions do more work than others with an instruction. Processor performance is also influenced by other factors like the instruction mix of the benchmark program, the addressing modes of the instructions used, or even the ability of the processor to execute several instructions simultaneously. Since the MIPS measurement doesn't take into account these and other factors, it isn't always a fair way to measure the performance of a computer system. A computer rated at 100 MIPS may be able to compute certain values faster than another computer rated at 120 MIPS.

For all the above reasons, MIPS ratings are not as often used today because of the development of other processor benchmarks that give a more accurate rating of a computerís performance. However, the MIPS measurement has been used by many computer manufacturers like IBM to measure the "cost of computing." The value of computers is determined in MIPS per dollar. Interestingly, the value of computers in MIPS per dollar has steadily doubled on an annual basis for the last couple of decades. As an example of the advancement of CPU speed over the last two decades, The Motorola 68000 processor 1979 ran at 1 MIPS at 8 Mhz in the year 1979 as compared to the Intel Core 2 X6800 processor which ran at 27,079 MIPS at 2.93 Ghz in 2006.