Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

QuT: A Low-Power Optical Network-on-chip

Parisa Khadem Hamedani

Natalie Enright Jerger

Shaahin Hessabi

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Introduction: Electrical NoC Electrical NoC

Scalability limitation Power

Network channel and buffering power Latency

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Introduction: Optical NoC Optical NoC

Power is independent of transmission distance Small transmission latency Simple modulation, large data bandwidths (Gbps)

Transmitter

Receiver

Off-chip Laser

Waveguide

Optical Switches

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Introduction: Optical NoC Challenges Optical NoC

Insertion Loss The loss of signal power resulting from the insertion in

an optical path Main factor in the power consumption

Number of Microrings Major source of faults

Number of Wavelengths Wavelength-division multiplexing (WDM) Total power is proportional to the number of

wavelengths

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Introduction: Quarten Topology (QuT)

0

2

1

3

4

6

5

78

10

9

11

12

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13

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Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Outline Introduction Quartern Architecture

Data Network Router Microarchitecture

Wavelength assignment All optical switches

QuT WDM Routing Control Network

Methodology Evaluation Conclusion

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Quartern Architecture A new all-optical architecture

Based on passive microring resonators Addressing the optical challenges

Ring-based topology Strategically placed extra links

To reduce the diameter To reduce number of wavelengths

A new deterministic wavelength routing Contention-free network Optimizing optical switches

With an optical control network

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Data Network

Ring links Bidirectional

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2

1

3

4

6

5

78

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9

11

12

14

13

15

Cross links Bidirectional Even

Bypass links Unidirectional Emanate from odd nodes

Cross

Bypass

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Router Microarchitecture : Wavelength assignment Each node has:

Dedicated but not unique wavelength Source uses this wavelength

In an N-node QuT N/4 distinct wavelength sets Node i dedicated wavelength set

(i mod N/4)

λ1λ0

λ2

λ3

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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QuT WDM Routing : Source is even Distance (Source, Destination):

< N/4 = N/2

Ring links

Source

Destination

0

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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QuT WDM Routing : Source is even Distance (Source, Destination):

>= N/4

Cross links

Source

Destination

0

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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QuT WDM Routing : Source is Odd Distance (Source, Destination):

<= N/4

Ring links

Source

Destination

1

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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QuT WDM Routing : Source is Odd Distance (Source, Destination):

> N/4

Bypass links

Source

Destination

1

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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QuT WDM Routing: example

0

8

Source: N0Destination: N8

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Example: Switch at N0

Ring (Left)

Bypass (Left)

Cross (Left)

Cross (Right)

Ring (Right)

Bypass (Right)

I1

I2

I3

I401

8

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Example: Switch at N1

0

21

8

Ring (Left)

Ring (Right)

Bypass (Left)

Bypass (Right)

I1

I2

I3

I4

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Example: Switch at N2

0

21

6

8

Ring (Left)

Bypass (Left)

Cross (Left)

Cross (Right)

Ring (Right)

Bypass (Right)

I1

I2

I3

I4

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Example: Switch at N6

0

6

7 8

Ring (Left)

Bypass (Left)

Cross (Left)

Cross (Right)

Ring (Right)

Bypass (Right)

I1

I2

I3

I4

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Example: Switch at N7

0

21

67 8

Ring (Left)

Ring (Right)

Bypass (Left)

Bypass (Right)

I1

I2

I3

I4

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Example: Switch at N8

0

21

6

7 8

Ring (Left)

Bypass (Left)

Cross (Left)

Cross (Right)

Ring (Right)

Bypass (Right)

I1

I2

I3

I4

E

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Router Microarchitecture: All optical switches (Even)

AddμR BypassμR DropμR

Ring (Left)

Bypass (Left)

Cross (Left)

Cross (Right)

Ring (Right)

Bypass (Right)

I1

I2

I3

I4

E

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Router Microarchitecture: All optical switches (Even)

Ring (Left)

Bypass (Left)

Cross (Left)

Cross (Right)

Ring (Right)

Bypass (Right)

I1

I2

I3

I4

E

AddμR

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Router Microarchitecture: All optical switches (Even)

Ring (Left)

Bypass (Left)

Cross (Left)

Cross (Right)

Ring (Right)

Bypass (Right)

I1

I2

I3

I4

E

BypassμR

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Router Microarchitecture: All optical switches (Even)

Ring (Left)

Bypass (Left)

Cross (Left)

Cross (Right)

Ring (Right)

Bypass (Right)

I1

I2

I3

I4

E

DropμR

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Router Microarchitecture: All optical switches (Odd)

Ring (Left)

Ring (Right)

Bypass (Left)

Bypass (Right)

I1

I2

I3

I4

E

AddμR CrossμR DropμR

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Router Microarchitecture: All optical switches (Odd)

Ring (Left)

Ring (Right)

Bypass (Left)

Bypass (Right)

I1

I2

I3

I4

E

AddμR DropμR

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Router Microarchitecture: All optical switches (Odd)

Ring (Left)

Ring (Right)

Bypass (Left)

Bypass (Right)

I1

I2

I3

I4

E

CrossμR

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Control Network Multiple-Writer Single-Reader bus

Multiple waveguides Control Packets

Request, ACK, NACK Small size: 6 bits

Each source node has a dedicated wavelength In an N-node QuT

N/16 waveguides N wavelengths

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Methodology Phoenixsim

An event-driven simulator Based on OMNet++

64 and 128-node QuT compared against

Topology Number of Wavelength

s

Control Network

λ-router N -Optical Spidergon:

Ring-basedN/2 Optical

Corona: Optical crossbar 8 Slot-token-ring

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Outline Introduction Quartern Architecture Methodology Evaluation

Delay Power Energy Throughput Area

Conclusion

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Evaluation Constant optical bandwidth for all-optical

NoCs Each node has 8 distinct wavelengths

Data stream is modulated on 8 wavelengths assigned to the destination

Die size: 225 mm Packet size: 256 bits 10Gb/s modulator and detector Synthetic traffic patterns:

Random, Bitreverse, Neighbor, Tornado and Hotspot-30%

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Delay: Packet latency (cycle)

Random Neighbor Tornado Bitreverse05

101520253035

QuT

Spider

Corona

128-node:

Offered Load = 0.5

Waiting time in a processor’s output bufferThe delay of modulating the packet

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Power (W)

QuT & CN Spidergon & CN

Corona & CN

λ-router0

5

10

15

20

25

64-node128-node

75.18

Small Insertion loss, Small number of required wavelengths,

Small number of microrings

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Energy-per-bit (pJ)

0

40

80

120

160

200

240

280

QuT

Spidergon

Corona

λ-router

128-node:

Lower power dissipationSmaller average optical path delay

At the saturation point, a small fraction of energy-per-bit is related to data network

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Normalized Throughput-per-watt

0.00.20.40.60.81.0

QuTSpi-dergonCoronaλ-router

0.00.51.01.52.02.5

QuTSpidergonCoronaλ-router

128-node:

64-node:

Better throughput-per-watt, when the network size increases

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Normalized Area

64-node 128-node0

0.5

1

1.5

2

2.5

3

QuT & CN

Spidergon & CN

λ-Router

Corona & CN

154%

44%

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Conclusion Considering optical challenges

Insertion loss Number of microrings Number of wavelengths

Topology Insertion Loss

Number of Wavelengt

hs

Number of Microrings

Control Network

QuT Small N/4 Small Optical

λ-router Large N Largest -

Spidergon Smallest N/2 Large Optical

Corona Largest 8 Smallest Slot-token-ring

Consuming Less power and Energy: Scales better than state-of-art

proposals

Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip

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Thank you for your attention!Question?