CLOCKLESS CHIPS

How fast is your personal computer? When people ask this ques tion, 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 tak es plac e 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 t iming signals. The use of a central clock also creates problems. As

speeds have increased, distributing the timing signals has become

more and more difficult. Present-day transistors can process data so

quick ly that they can accomplish several steps in the time that it takes

a wire to carry a signal from one side of the chip to the other. Keeping

the rhythm identical in all parts of a large chip requires careful design

and a great deal of electric al power. Wouldn't it be nice to have an

alternative? Clockless approach, which uses a technique known as

asynchronous logic, differs from conventional computer circuit design

in that the switching on and off of digital circuits is controlled

individually by specific pieces of data rather than by a tyrannical clock

that forces all of the millions of the circuits on a chip to march in

unison. It overcomes all the disadvantages of a clocked circuit such

as slow speed, high power c onsumption, high electromagnetic noise

etc.

For these reasons the clockless technology is

considered as the technology which is going to drive majority of

electronic chips in the coming years.