introduction to interconnection networks. introduction to interconnection network digital...
TRANSCRIPT
![Page 1: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/1.jpg)
Introduction to Interconnection Networks
![Page 2: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/2.jpg)
Introduction to Interconnection network
• Digital systems(DS) are pervasive in modern society.
• Digital computers - simulating physical systems, managing large databases , preparing documents and etc
• Audio and video entertainment is increasingly being delivered and processed in digital form.
Finally, almost all products from automobiles to home appliances are digitally controlled.
![Page 3: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/3.jpg)
Digital Systems
Communication (Moves Data)
Memory(Stores Data)
Logic(Transfers and combines
Data)
![Page 4: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/4.jpg)
Digital Systems
Logic(Transfers and combines
Data)
Memory(Stores Data)
Communication (Moves Data)
Interconnection Network
![Page 5: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/5.jpg)
• Performance – limited by communication/interconnection not logic/memory
• Power - most of the clock cycle spent on wire delays not gate delay.
• Technology improves, memories and processors become small, fast, and inexpensive.
• Also, the frequency of communication between components is lagging far beyond the clock rates of modern processors.
• These factors combine to make interconnection the key factor in the success of future digital systems.
![Page 6: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/6.jpg)
Interconnection Network
ApplicationAlgorithmProgramming LanguageOperating SystemInstruction Set Architecture Micro-architectureRegister Transfer Level
CircuitsDevicesTechnology
Com
pute
r Arc
hite
ctur
e Logic Mem MemLogic
Logic MemLogicMem
Interconnection Network
![Page 7: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/7.jpg)
Network Scenario• “On-chip networks may deliver data between
memory arrays, registers, and arithmetic units within a single processor “
![Page 8: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/8.jpg)
Why Networks ?
Computing demandsProcessors requirements
What is the Solution ?
![Page 9: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/9.jpg)
Three question about Interconnection Networks
What is an Interconnection Network ?
An Interconnection Network is a programmable system that transports data between terminal.
![Page 10: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/10.jpg)
Where do you find Interconnection Network ?
• They are used in almost all digital systems that are large
enough to have two components to connect.
• The most common applications computer systems and
communication switches
• Computer System - they connect processors to memories and
input/output (I/O) devices to I/O controllers
• Communication Switches - They connect input ports to output
ports
![Page 11: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/11.jpg)
Why are interconnection networks important ?
• Because they are a limiting factor in the performance of
many systems
• The interconnection network between processor and
memory largely determines the memory latency and
memory bandwidth, two key performance factors, in a
computer system of many systems
• The performance of the interconnection network in a communication
switch largely determines the capacity (data rate and number of
ports) of the switch
![Page 12: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/12.jpg)
Why on-chip networks ?• They provide external connectivity from system to outside
world Also, connectivity within a single computer system at
many levels I/O units , chips, modules and blocks inside chips
• Trends: high demand on communication bandwidth Increased computing power and storage capacity Switched networks are replacing buses
• Integral part of many-core architectures Energy consumed by communication will exceed that of
computation in future systems
![Page 13: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/13.jpg)
NoC: A paradigm Shift in VLSI
s
s
s
s
s s
s
s
Module
Module
s
Module
From: Dedicated signal wires To: Shared network
Network switch
Computing Module
Point to Point Link
![Page 14: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/14.jpg)
Processingelement
NetworkInterface
Router
Inputbuffers
Unidirectionallinks
NoC Architecture
![Page 15: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/15.jpg)
Perspective 1: NoC vs. Bus
• Aggregate bandwidth grows
• Link speed unaffected by N• Concurrent spatial reuse• Pipelining is built-in• Distributed arbitration
However:• No performance guarantee• Extra delay in routers• Area and power overhead?• Modules need NI • Unfamiliar methodology
Bandwidth is shared Speed goes down as N
grows No concurrency Pipelining is tough Central arbitration
However: Fairly simple and familiar
NoC Bus
A B
E
C
D
Shared Bus
![Page 16: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/16.jpg)
Perspective 2: NoC vs. Off-chip Networks
• Cost is in the links• Latency is tolerable• Traffic/applications
unknown• Changes at runtime• Adherence to
networking standards
Sensitive to cost: area power
Wires are relatively cheap
Latency is critical
Traffic may be known a-priori
Design time specialization
Custom NoCs are possible
Example:
Off-Chip NetworksNoC
M odule
M odule M odule
M odule M odule
M odule M odule
M odule
M odule
M odule
M odule
M odule
M odule
M odule M odule
M odule M odule
M odule M odule
M odule
M odule
M odule
M odule
M odule
![Page 17: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/17.jpg)
Performance Metrics:
• Packet Latency
• Effective Bandwidth
![Page 18: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/18.jpg)
Terms and Definitions:
• Bandwidth: Maximum rate at which information can be transferred (including packet header, payload and trailer)
Unit: bits per second (bps) or bytes per second (Bps)
• Time of flight: Time for first bit of a packet to arrive at the receiver
Includes the time for a packet to pass through the network, not including the transmission time Unit: Picoseconds (OCNs), nanoseconds (SANs), microseconds (LANs), milliseconds (WANs)
![Page 19: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/19.jpg)
• Transmission time: The time for a packet to pass through the network, not including the time of flight
Equal to the packet size divided by the data bandwidth of the link
• Transport latency:Sum of the time of flight and the transmission time
Measures the time that a packet spends in the network
• Sending overhead (latency):Time to prepare a packet for injection, including hardware/software
A constant term (packet size) plus a variable term (buffer copies)
• Receiving overhead (latency):Time to process an incoming packet at the end node
A constant term plus a variable term Includes cost of interrupt, packet reorder and message reassembly
![Page 20: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/20.jpg)
Receiver
SenderSending
overheadTransmission time(bytes/bandwidth)
Time offlight
Transmission time(bytes/bandwidth)
Receivingoverhead
Transport latency
Total latency
Time
Latency = Sending Overhead + Time of flight + + Receiving Overhead packet size
Bandwidth
![Page 21: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/21.jpg)
Example (latency): calculate the total packet latency for interconnect distances of 0.5 cm, 5 m, 5,000 m, and 5,000 km
Assume a dedicated-link network with8 Gbps (raw) data bandwidth per linkDevice A sends 100-byte packets (header included)
OverheadsSending overhead: x + 0.05 ns/byteReceiving overhead: 4/3(x) + 0.05 ns/byte
x is 0 μs for OCN, 0.3 μs for SAN, 3 μs for LAN, 30 μs for WANAssume time of flight consists only of link propagation delay (no other sources of delay)
int. networkint. network
Device ADevice A Device BDevice B
8 Gbps raw data bandwidth per link
Cr
![Page 22: Introduction to Interconnection Networks. Introduction to Interconnection network Digital systems(DS) are pervasive in modern society. Digital computers](https://reader035.vdocuments.us/reader035/viewer/2022062421/56649e245503460f94b132b4/html5/thumbnails/22.jpg)
int. networkint. network
Device ADevice A Device BDevice B
8 Gbps raw data bandwidth per link
Cr
LatencyOCN = 5 ns + 0.025 ns + 100 ns + 5 ns = 110.025 ns
LatencySAN = 0.305 μs + 0.025 ns + 0.1 μs + 0.405 μs = 0.835 μs
LatencyLAN = 3.005 μs + 25 μs + 0.1 μs + 4.005 μs = 32.11 μs
LatencyWAN = 20.05 μs + 25 μs + 0.1 μs + 40.05 μs = 25.07 ms
Latency = Sending overhead + Time of flight +Packet sizeBandwidth + Receiving overhead