(Million Instructions Per Second) The execution speed of a computer. For example, .5 MIPS is 500,000 instructions per second; 100 MIPS is a hundred million instructions per second. MIPS was a popular rating before computers reached gigahertz speeds, but MIPS rates were never uniform. Some were best-case mixes while others were averages. In addition, it takes more instructions in one machine to do the same thing as another (RISC vs. CISC, mainframe vs. PC). As a result, MIPS has been called "MisInformation to Promote Sales" as well as "Meaningless Interpretation of Processor Speed." See also MIPS Technologies.

MIPS and MHz
There is a mathematical relationship between MIPS and MHz. You can derive MIPS from MHz if you know how many machine cycles it takes to execute an instruction in the CPU. For example, a 486 takes 1.9 cycles on average. To obtain MIPS on a 50 MHz 486, you would divide 50 by 1.9, yielding 26 MIPS (rather paltry by today's standards).