Clockless Chip
CHAPTER 1
INTRODUCTION
1.1 Introduction
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.
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 quickly 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 electrical power. Wouldn 't it be nice to have an alternative?
Clock less 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 consumption, high electromagnetic noise etc.
For these reasons the clock less technology is considered as the technology which is going to drive majority of electronic chips in the coming years.
1.2 Clock Concept
The clock is a tiny crystal oscillator that resides in the heart of every microprocessor chip. The clock is what which sets the basic rhythm used throughout the machine. The clock orchestrates the synchronous dance of electrons that course through the hundreds of millions of wires and transistors of a modern computer.
Such crystals which tick up to 2 billion times each second in the fastest of today 's desktop personal computers, dictate the timing of every circuit in
INTRODUCTION
1.1 Introduction
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.
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 quickly 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 electrical power. Wouldn 't it be nice to have an alternative?
Clock less 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 consumption, high electromagnetic noise etc.
For these reasons the clock less technology is considered as the technology which is going to drive majority of electronic chips in the coming years.
1.2 Clock Concept
The clock is a tiny crystal oscillator that resides in the heart of every microprocessor chip. The clock is what which sets the basic rhythm used throughout the machine. The clock orchestrates the synchronous dance of electrons that course through the hundreds of millions of wires and transistors of a modern computer.
Such crystals which tick up to 2 billion times each second in the fastest of today 's desktop personal computers, dictate the timing of every circuit in
References: [1] C. H. (Kees) van Berkel, Mark B. Josephs, and Steven M. Nowick proceedings of IEEE Scanning the Technology: Applications of Asynchronous Circuits, December 1998. [2] Ivan E Sutherland and Jo Ebergen Scientific American, Computers without clocks August 2002. [3] David Geer, Is it time for Clock less chips? Published by IEEE Computer Society, March 2005. [4] Guest Editors’ Introduction: Clock less VLSI Systems – Soha Hassoun,Yong-Bin Kim and Fabrizio Lombardi co published by IEEE CS and IEEE November – December 2005. [5] Claire Tristram from MIT Technology, It 's Time for Clockless Chips, October 2001 [6] Old tricks for new chips Apr 19th 2001 From The Economist print edition.