MIPS

  ``millions of instructions per second''

``MIPS'' is a popular metric for performance - the customer knows what is means, and more is better.

$${\rm MIPS} = \frac{{\rm instruction~count}} {{\rm execution~time} \times 10^6}$$

• depends on instruction set

• depends on the program (why?)

• decreasing MIPS can mean increased performance

HOW ?

• Modifying the hardware to introduce powerful instructions (e.g. floating point) reduces the number of instruction executed, but may improve performance.

• If an optimising compiler avoids the need for some instructions, it changes the MIPS rating (increases? or decreases?)

(See Hennessy & Patterson page 44)