CLOCKLESS CHIPS

BY- SAURABH SINGHEC III (B)

1016431096PSIT,KANPUR

PRESENTATION FLOW:

Introduction. Concept of clock Problems with synchronous circuits. Clockless / Asynchronous circuits. How clockless chips work? Simplicity in design. Advantages Recent Commercial Interest Challenges. Conclusion References

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INTRODUCTION.

Struggle for the improvement in the

microprocessor’s performance/functioning.

Pipelining

(Simultaneous) Multithreading

Clockless / Asynchronous logic

Synchronous

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CONCEPT OF CLOCK:

Tiny crystal oscillator.

Sets basic rhythm used throughout the machine. The system clock for an integrated circuit is a voltage

signal that pulses at a regular frequency.1

0 The clock tells each stage of a circuit that the inputs of

that stage are valid and can be processed.

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PROBLEMS WITH SYNCHRONOUS APPROACH

o Clock distribution: requires significant designer effort.

o Wastage of energy.

o Clock burns large fraction of chip power (~40-70%).

o Fixed clock rate: poor match foro designing reusable componentso interfacing with mixed-timing environments

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

o Order of arrival of the signals is unimportant.

o Distributing the clock globally.

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CLOCKLESS CHIPS (ASYNCHRONOUS LOGIC CIRCUITS)

Clockless chips/Asynchronous/self-timed circuits.

Functions away from the clock.

Different parts work at different speeds.

Hand-off the result immediately.

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HOW DO THEY WORK?

No centralized clock required.

Data moves only when required, not always.

Minimizes power consumption.

Less EMI less noise more applications.

Stream data applications. Uses handshake signals for the data exchange.

HOW HANDSHAKING WORKS

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Processing Data Idle

Stage 1 Stage 2

HOW HANDSHAKING WORKS

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TransmittingData

Idle

Request

Data

Stage 1 Stage 2

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HOW HANDSHAKING WORKS

TransmittingData

DataReceived

Request

Acknowledge

Data

Stage 1 Stage 2

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HOW HANDSHAKING WORKS

IdleProcessing

Data

Stage 1 Stage 2

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DIFFERENT STYLES: Simplest implementation of asynchronous

design.

Assumption: we know the largest amount of time for each component to perform its task.

Very similar to synchronous design.

Function delay is introduced here.

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ADVANTAGES Works at increased speed (2.8 times). Low power consumption.

• Twice life-time. Less heat generated.

• Good to mobile devices. Less EMI less noise more applications.

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RECENT COMMERCIAL INTEREST

Several commercial asynchronous chips:Philips: asynchronous 80c51 microcontrollersUniv. of Manchester: async ARM996HS processor

[2006]Motorola: async divider in PowerPC chip [2000]HAL: async floating-point divider

Recent experimental chips: IBM, Sun and Intel: IBM/Columbia/UNC: asynchronous digital FIR filter

Several recent startups:Theseus Logic, Fulcrum, Self-Timed Solutions

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CHALLENGES Interfacing between synchronous and

asynchronousMany 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.

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CONCLUSION: Clocks are getting faster , while chips are getting

bigger both of which make clock distribution harder

There are also various other problems associated with it. So we could only get out of it , if more focus , especially at the university level is given to the asynchronous design.

It is certainly a challenge , but as software community is moving towards concurrency, hardware community must move to incorporate asynchronous logic.

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REFERENCES Google Wikipedia Digital Design—MORIS MANO Digital Circuits & Design—SALIVAHANAN www.technologyreview.com www.seminarprojects.com www.slideshares.net www.handshakesolutions.com

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Any queries

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THANKS