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

QuT: A Low-Power Optical Networkon-chip
Parisa Khadem Hamedani
Natalie Enright Jerger
Shaahin Hessabi
Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip
Introduction: Electrical NoC

Electrical NoC

Scalability limitation

Power


Network channel and buffering power
Latency
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Introduction: Optical NoC

Optical NoC



Power is independent of transmission distance
Small transmission latency
Simple modulation, large data bandwidths (Gbps)
Off-chip
Laser
Transmitter
Waveguide
Optical
Switches
Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip
Receiver
3
Introduction: Optical NoC Challenges

Optical NoC

Insertion Loss



Number of Microrings


The loss of signal power resulting from the insertion in an optical path
Main factor in the power consumption
Major source of faults
Number of Wavelengths


Wavelength-division multiplexing (WDM)
Total power is proportional to the number of wavelengths
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Introduction: Quarten Topology (QuT)
1
0
14
2
3
12
4
5
8
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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
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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



A new deterministic wavelength routing



To reduce the diameter
To reduce number of wavelengths
Contention-free network
Optimizing optical switches
With an optical control network
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Data Network

Ring links

Bypass
1
Bidirectional
0
14
2

Cross links



Bidirectional
Even
Bypass links


3
Cross
12
4
5
Unidirectional
Emanate from odd nodes
8
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


λ1
N/4 distinct wavelength sets
Node i dedicated wavelength set

(i mod N/4)
Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip
λ0
λ2
λ3
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QuT WDM Routing : Source is even

Distance (Source, Destination):
 < N/4
 = N/2

Ring links
0
Source
Destination
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QuT WDM Routing : Source is even

Distance (Source, Destination):
 >= N/4

Cross links
0
Source
Destination
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QuT WDM Routing : Source is Odd

Distance (Source, Destination):
 <= N/4

Ring links
1
Source
Destination
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QuT WDM Routing : Source is Odd

Distance (Source, Destination):
 > N/4

Bypass links
1
Source
Destination
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QuT WDM Routing: example
0
8
Source: N0
Destination: N8
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Example: Switch at N0
1
I1
0
I2
I3
I4
Ring
(Left)
Bypass
(Left)
Ring
(Right)
Bypass
(Right)
8
Cross
(Left)
Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip
Cross
(Right)
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Example: Switch at N1
1
0
2
I1
Ring
(Left)
8
Bypass
(Left)
Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip
I2
I3
I4
Ring
(Right)
Bypass
(Right)
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Example: Switch at N2
1
I1
0
I2
I3
I4
2
Ring
(Left)
Bypass
(Left)
Ring
(Right)
Bypass
(Right)
8
Cross
(Left)
Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip
Cross
(Right)
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Example: Switch at N6
I1
0
I2
I3
I4
Ring
(Left)
Bypass
(Left)
Ring
(Right)
Bypass
(Right)
8
Cross
(Left)
Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip
Cross
(Right)
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Example: Switch at N7
1
0
2
I1
Ring
(Left)
8
Bypass
(Left)
Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip
I2
I3
I4
Ring
(Right)
Bypass
(Right)
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Example: Switch at N8
1
I1
0
I2
E
I3
I4
2
Ring
(Left)
Bypass
(Left)
Ring
(Right)
Bypass
(Right)
8
Cross
(Left)
Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip
Cross
(Right)
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Router Microarchitecture: All optical
switches (Even)
I1
I2
E
I3
I4
Ring
(Left)
Ring
(Right)
Bypass
(Left)
Bypass
(Right)
Cross
(Left)
AddμR
Cross
(Right)
BypassμR
Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip
DropμR
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Router Microarchitecture: All optical
switches (Even)
I1
I2
E
I3
I4
Ring
(Left)
Ring
(Right)
Bypass
(Left)
Bypass
(Right)
Cross
(Left)
Cross
(Right)
AddμR
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Router Microarchitecture: All optical
switches (Even)
I1
I2
E
I3
I4
Ring
(Left)
Ring
(Right)
Bypass
(Left)
Bypass
(Right)
Cross
(Left)
Cross
(Right)
BypassμR
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Router Microarchitecture: All optical
switches (Even)
I1
I2
E
I3
I4
Ring
(Left)
Ring
(Right)
Bypass
(Left)
Bypass
(Right)
Cross
(Left)
Cross
(Right)
DropμR
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Router Microarchitecture: All optical
switches (Odd)
I1
I2
E
I3
Ring
(Left)
Ring
(Right)
Bypass
(Right)
Bypass
(Left)
AddμR
I4
CrossμR
Khadem Hamedani et al., QuT: A Low Power Optical Network-on-Chip
DropμR
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Router Microarchitecture: All optical
switches (Odd)
I1
I2
E
I3
I4
Ring
(Left)
Ring
(Right)
Bypass
(Right)
Bypass
(Left)
AddμR
DropμR
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Router Microarchitecture: All optical
switches (Odd)
I1
I2
E
I3
Ring
(Left)
I4
Ring
(Right)
Bypass
(Right)
Bypass
(Left)
CrossμR
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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
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Methodology

Phoenixsim



An event-driven simulator
Based on OMNet++
64 and 128-node QuT compared against
Topology
Number of
Wavelengths
Control Network
λ-router
N
-
Optical Spidergon: Ring-based
N/2
Optical
Corona: Optical crossbar
8
Slot-token-ring
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Outline




Introduction
Quartern Architecture
Methodology
Evaluation






Delay
Power
Energy
Throughput
Area
Conclusion
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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%
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Delay: Packet latency (cycle)
128-node:
35
30
25
20
15
10
5
0
QuT
Spider
Corona
λ-router
Random
Neighbor
Tornado
Bitreverse
Offered Load = 0.5
Waiting time in a processor’s output buffer
The delay of modulating the packet
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Power (W)
25
75.18
20
15
64-node
10
128-node
5
0
QuT & CN
Spidergon &
CN
Corona & CN
λ-router
Small Insertion loss,
Small number of required wavelengths,
Small number of microrings
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Energy-per-bit (pJ)
280
240
128-node: 200
QuT
160
Spidergon
120
Corona
80
λ-router
40
0
Random Neighbor Tornado Bitreverse HotSpot HotSpot
before
at
saturation saturation
Lower power dissipation
Smaller average optical path delay
At the saturation point, a small fraction of energy-per-bit is
related to data network
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Normalized Throughput-per-watt
64-node:
2.5
2.0
1.5
1.0
0.5
0.0
QuT
Spidergon
Corona
λ-router
Random Neighbor Tornado
Bitreverse
Better throughput-per-watt,
when
the HotSpot
network
size
before
increases
saturation
128-node:
1.0
0.8
0.6
0.4
0.2
0.0
QuT
Spidergon
Corona
λ-router
Random Neighbor Tornado Bitreverse HotSpot
before
saturation
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Normalized Area
3
154%
2.5
44%
2
QuT & CN
1.5
Spidergon & CN
1
λ-Router
0.5
Corona & CN
0
64-node
128-node
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Conclusion

Considering optical challenges



Insertion loss
Number of microrings
Number of wavelengths
Topology
Insertion
Loss
Number of
Wavelengths
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
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Thank you for your attention!
Question?
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