• The two major styles of I/O are polled and interrupt driven.

• Interrupts may be vectorized and prioritized.

• Supervisor mode helps protect the computer from program errors and provides a mechanism for controlling multiple programs.

• An exception is an internal error; a trap or software interrupt is explicitly generated by an instruction. Both are handled similarly to interrupts.

• A cache provides fast storage for a small number of main memory locations. Caches may be direct mapped or set associative.

• A memory management unit translates addresses from logical to physical addresses.

• Co-processors provide a way to optionally implement certain instructions in hardware.

• Program performance can be influenced by pipelining, superscalar execution, and the cache. Of these, the cache introduces the most variability into instruction execution time.

• CPUs may provide static (independent of program behavior) or dynamic (influenced by currently executing instructions) methods for managing power consumption.