ADVOCATE FOR ASYNCHRONY: Ivan E. Sutherland, one of the authors of this article, has been called "the father of computer graphics." Now the leader of a research group at Sun Microsystems Laboratories, he holds a silicon wafer containing UltraSPARC IIIi processor chips, which use some asynchronous circuits. Image: OLIVIER LAUDE; COPYRIGHT IS HELD BY SUN MICROSYSTEMS,INC.
SUN, SUN MICROSYSTEMS, INC., AND UltraSPARC ARE REGISTERED TRADEMARKS OF SUN IN THE U.S. AND OTHER COUNTRIES
How fast is your personal computer?
When people ask this question, they are typically referring to the frequency of a minuscule clock inside the computer, a crystal oscillator that sets the basic rhythm used throughout the machine. In a computer with a speed of one gigahertz, for example, the crystal "ticks" a billion times a second. Every action of the computer takes place in tiny steps, each a billionth of a second long. A simple transfer of data may take only one step; complex calculations may take many steps. All operations, however, must begin and end according to the clock's timing signals.
This article was originally published with the title Computers without Clocks.