Clockless chips
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Date: October 26, 2005. Clockless Chips. Presented by: K. Subrahmanya Sreshti. (05IT6004) School of Information Technology Indian Institute of Technology, Kharagpur. Presentation flow:. Introduction. Problems with synchronous circuits. Clockless / Asynchronous circuits.

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Clockless Chips

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Clockless chips

Date: October 26, 2005.

Clockless Chips

Presented by:

K. Subrahmanya Sreshti.

(05IT6004)

School of Information Technology

Indian Institute of Technology, Kharagpur


Presentation flow

Presentation flow:

  • Introduction.

  • Problems with synchronous circuits.

  • Clockless / Asynchronous circuits.

  • How clockless chips work?

  • Simplicity in design.

  • Applications.

  • Applications (technical perspective).

  • Challenges.

Presentation on Clockless Chips


Introduction

Introduction.

  • Struggle for the improvement in the microprocessor’s performance/functioning.

    • Pipelining

    • (Simultaneous) Multi-threading

    • Clockless / Asynchronous logic

}Synchronous

Presentation on Clockless Chips


Problems with synchronous approach

Problems with Synchronous Approach

  • Distributing the clock globally.

  • Wastage of energy.

  • Traverse the chip’s longest wires in one clock cycle.

  • Order of arrival of the signals is unimportant.

  • Clocks themselves consume lot of energy (~30%).

Presentation on Clockless Chips


Synchronous circuit

Synchronous circuit

  • Longest path determines the minimum clock period.

  • Dissipation of energy for each clock cycle.

  • EMI is more in synchronous elements.

Presentation on Clockless Chips


Clockless chips asynchronous logic circuits

Clockless chips (Asynchronous logic circuits)

  • Colckless chips/Asynchronous/self-timed circuits.

  • Functions away from the clock.

  • Different parts work at different speeds.

  • Hand-off the result immediately.

Presentation on Clockless Chips


Clock time cycle vs clockless time cycle

Clock time cycle vs. clockless time cycle

Courtesy: Fulcrum Microsystems.

Presentation on Clockless Chips


Courtesy computers without clocks ivan e sutherland and jo ebergen

Courtesy: Computers without clocks – Ivan E Sutherland and Jo Ebergen

Presentation on Clockless Chips


How do they work

How do they work?

  • No pure asynchronous chips are available.

  • Uses handshake signals for the data exchange.

  • Data moves only when required, not always.

    • Minimizes power consumption.

    • Less EMI  less noise  more applications.

    • Stream data applications.

Presentation on Clockless Chips


Simple and efficient design

Simple and efficient design

  • No centralized clock required.

  • Standardized components can be used.

Presentation on Clockless Chips


Some features

Some features

  • Integrated pipelining mode.

    • Domino logic.

    • Delay – insensitive.

  • Two different implementation details

    • Dual rail.

    • Bundled data.

Presentation on Clockless Chips


Advantages

Advantages

  • Works at its average speed.

  • Low power consumption.

    • Twice life-time.

  • Less heat generated.

     Good to mobile devices.

  • Less EMI  less noise  more applications.

  • Smart cards (due to asynchronous nature).

Presentation on Clockless Chips


Advantages technical look

Advantages (technical look)

  • Asynchronous for higher performance:

    • Data-dependent delays.

    • All carry bits need to be computed.

Presentation on Clockless Chips


Advantages technical look1

Advantages (technical look)…

  • Asynchronous for low power:

    • Consumes power only when and where active.

    • Rest of the time returns to a non-dissipating state, until next activation.

    • Illustrated through frequency divider

Presentation on Clockless Chips


Advantages technical look2

Advantages (technical look)…

  • Asynchronous for low power:

    • Almost fixed power dissipation is achieved.

    • Many applications such as:

      • Infrared communication receiver.

      • Filter bank for digital hearing.

      • In pagers.

      • Double battery life.

Presentation on Clockless Chips


Advantages technical look3

Advantages (technical look)…

  • Asynchronous for low noise and low emission:

    • Digital sub-circuits

      • Generates voltage noise (on power lines)

      • Induces current on silicon substrate.

      • Emits electromagnetic radiation at its clock frequency or its harmonics.

Presentation on Clockless Chips


Advantages technical look4

Advantages (technical look)…

  • Heterogeneous Timing:

    • Gate delays.

    • Interconnection delays.

    • Heterogeneous systems would increase the delays in the circuits.

Presentation on Clockless Chips


Challenges

Challenges

  • Interfacing between synchronous and asynchronous

    • Many devices available now are synchronous in nature.

    • Special circuits are needed to align them.

  • Lack of expertise.

  • Lack of tools.

  • Engineers are not trained in these fields.

  • Academically, no courses available.

Presentation on Clockless Chips


References

References

  • Scanning the Technology: Applications of Asynchronous Circuits – C. H. (Kees) van Berkel, Mark B. Josephs, and Steven M. Nowick

  • Computers without clocks – Ivan E Sutherland and Jo Ebergen.

  • http://ieeexplore.ieee.org/iel5/2/30617/01413111.pdf(October 2001)

  • http://csdl2.computer.org/comp/mags/dt/2003/06/d6005.pdf

  • http://www1.cs.columbia.edu/async/misc/technologyreview_oct_01_2001.html

  • http://www.technologyreview.com/articles/01/10/tristram1001.asp

  • http://www1.cs.columbia.edu/async/misc/economist/Economist_com.htm

Presentation on Clockless Chips


Thank you

Thank you

Presentation on Clockless Chips


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