clockless chips . presentation on clockless chips2 presentation flow: introduction. problems with...

Clockless ChipsClockless Chips

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Presentation on Clockless Chips 2

Presentation flow:Presentation flow:

Introduction. Problems with synchronous circuits. Clockless / Asynchronous circuits. How clockless chips work? Simplicity in design. Applications. Applications (technical perspective). Challenges.


Introduction.Introduction.

Struggle for the improvement in the microprocessor’s

performance/functioning.

– Pipelining

– (Simultaneous) Multi-threading

– Clockless / Asynchronous logic

}Synchronous


Problems with Synchronous ApproachProblems 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%).


Synchronous circuitSynchronous circuit

Longest path determines

the minimum clock

period.

Dissipation of energy for

each clock cycle.

EMI is more in

synchronous elements.


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.


Clock time cycle vs. clockless time cycleClock time cycle vs. clockless time cycle

Courtesy:Courtesy: Fulcrum Microsystems. Fulcrum Microsystems.


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


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.


Simple and efficient designSimple and efficient design

No centralized clock required.

Standardized components can be used.


Some featuresSome features

Integrated pipelining mode.

– Domino logic.

– Delay – insensitive.

Two different implementation details

– Dual rail.

– Bundled data.


AdvantagesAdvantages

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).


Advantages (technical look)Advantages (technical look)

Asynchronous for higher

performance:

– Data-dependent delays.

– All carry bits need to be

computed.


Advantages (technical look)…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



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.



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.



Heterogeneous Timing:

– Gate delays.

– Interconnection delays.

– Heterogeneous systems

would increase the delays in

the circuits.


ChallengesChallenges

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.


ReferencesReferences

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


Thank youThank you

clockless chips . presentation on clockless chips2 presentation flow: introduction. problems with...

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