Chapter 2. Multiprocessors Interconnection Networks

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1 Chapter 2 Multiprocessors Interconnection Networks

2 2.1 Taxonomy Interconnection Network Static Dynamic 1-D 2-D HC Bus-based Switch-based Single Multiple SS MS Crossbar

3 2.2 Bus-Based Dynamic Single Bus Systems Simplest way to connect multiprocessor systems. The use of local caches reduces the processormemory traffic. Size of such system varies between 2 and 50 processors. Single bus multiprocessors are inherently limited by: Bandwidth of bus. 1 processor can access the bus. 1 memory access can take place at any given time.

Size of such system varies between 2 and 50 processors.

4 2.2 Bus-Based Dynamic Single Bus Systems p p p 1 2 N 1 p N Shared Memory I/O

5 2.2 Bus-Based Dynamic Multiple Bus Systems Several parallel buses to interconnect multiple processors and multiple memory modules. Many connection schemes are possible. Examples: Multiple Bus with Full Bus Memory Connection (MBFBMC). Multiple Bus with Single Bus Memory Connection (MBSBMC). Multiple Bus with Partial Bus Memory Connection (MBPBMC). Multiple Bus with Class-based Bus Memory Connection (MBCBMC).

Examples: Multiple Bus with Full Bus Memory Connection (MBFBMC).

6 2.2 Bus-Based Dynamic Multiple Bus Systems: Multiple Bus with Full Bus Memory Connection (MBFBMC). P 1 P 2 P 3 P 4 P 5 P 6 M 1 M 2 M 3 M 4

7 2.2 Bus-Based Dynamic Multiple Bus Systems: Multiple Bus with Single Bus Memory Connection (MBSBMC). P 1 P 2 P 3 P 4 P 5 P 6 M 2 M 3 M 1 M 4

8 2.2 Bus-Based Dynamic Multiple Bus Systems: Multiple Bus with Partial Bus Memory Connection (MBPBMC). P 1 P 2 P 3 P 4 P 5 P 6 M 1 M 2 M 3 M 4

9 2.2 Bus-Based Dynamic Multiple Bus Systems: Multiple Bus with Class-based Memory Connection (MBCBMC). P 1 P 2 P 3 P 4 P 5 P 6 M 1 M 2 M 3 M 4 M 5 M 6 Class 1 Class 2 Class 3

10 2.2 Bus-Based Dynamic Bus Synchronization A bus can be synchronous: Time for any transaction is known in advance. A bus can be asynchronous: Depends on the availability of data and readiness of devices to initiate bus transactions. Bus arbitration logic is required to resolve bus contention when more than 1 processor compete to access the bus in single bus multiprocessor. Process of passing mastership from 1 processor to another is called handshaking Requires a bus request and a bus grant.

Bus arbitration logic is required to resolve bus contention when more than 1 processor compete to access the bus in single

11 2.2 Bus-Based Dynamic Bus Synchronization Bus arbitration logic uses a a predefined priority scheme: Random Simple rotating Equal priority Least Recently Used (LRU)

12 2.3 Switch-Based Interconnection Crossbar Networks Networks Provide simultaneous connections among all its inputs and all its outputs. A Switching Element (SE) is at the intersection of any 2 lines extended horizontally or vertically inside the switch. It is a non-blocking network allowing multiple inputoutput connection pattern to be achieved simultaneously.

A Switching Element (SE) is at the intersection of any 2 lines extended horizontally or

13 2.3 Switch-Based Interconnection Networks Crossbar Networks P1 P2 P3 P4 P5 P6 P7 P8 M1 M2 M3 M4 M5 M6 M7 M8 Straight Switch Setting Diagonal Switch Setting

14 2.3 Switch-Based Single-Stage Networks A single stage of SE exists between the inputs and outputs of the network. Possible settings of a 2x2 SE are: Straight Exchange Upper-broadcast Lower-broadcast

15 2.3 Switch-Based Multistage (MINs) A MIN consists of a number of stages each consisting of a set of 2x2 SEs. Stages are connected to each other using Inter-Stage Connection (ISC) pattern. In MINs the routing of a message from a given source to a given destination is based on the destination address (self-routing).

Stages are connected to each other using Inter-Stage Connection (ISC) pattern.

16 2.3 Switch-Based Multistage Networks (MINs) ISC 1 ISC x-1 Switches (Stage 1) Switches (Stage 2) Switches (Stage x)

17 2.3 Switch-Based Blockage in Multistage Interconnection Networks Blocking networks: when an interconnection between a pair of input/output is currently established, the arrival of a request for a new interconnection between 2 arbitrary unused input and output may or may not be possible.

input/output is currently established, the arrival of a request for a

18 2.3 Switch-Based Blockage in Multistage Interconnection Networks Rearrangeable networks: Always possible to rearrange already established connections in order to make allowance for other connections to be established simultaneously

rearrange already established connections in order to

19 2.3 Switch-Based Blockage in Multistage Interconnection Networks Rearrangeable networks

001 010 011 100 101 110 111 000 001 010 011 100 101

20 2.3 Switch-Based Blockage in Multistage Interconnection Networks Non-blocking networks: In presence of a currently established connection between any pair of input/output, it is always possible to establish a connection between any arbitrary unused pair of input/output.

connection between any pair of input/output, it is always possible

21 2.3 Switch-Based Blockage in Multistage Interconnection Networks Non-blocking networks:

22 2.3 Switch-Based Interconnection Networks

23 2.4 Static Have fixed paths, unidirectional or bidirectional, between processors. Types: Completely connected networks: Number of links: O(N 2 ), delay complexity: O(1) completely connected network. 5 4

24 2.4 Static Limited Connection Networks: Linear arrays Ring (Loop) networks Two-dimensional arrays Tree networks Cube network

25 2.4 Static Linear arrays Ring (Loop) networks Two-dimensional arrays Tree networks Cube network

26 2.4 Static Cube Connected Networks: Patterned after the n-cube structure In an n-cube, every processor is connected to n others Ex: a 4-cube: S

27 2.4 Static Mesh Connected Networks: D D S S Example 3X3X2 mesh network

28 2.5 Analysis and Performance Dynamic Networks Metrics Networks Delay Cost Blockin g Degree of FT Bus O(N) O(1) Yes 0 Multiple-bus O(mN) O(m) Yes (m-1) MIN O(logN) O(NlogN) Yes 0 Crossbar O(1) O(N 2 ) No 0

29 2.5 Analysis and Performance Static Networks Metrics Networks Degree (d) Diameter (D) Cost (No. of links) Symmetry Worst Delay CCNs N-1 1 N(N-1)/2 Yes 1 Linear array 2 N -1 N -1 No N Binary tree 3 Log N -1) 2( 2 N -1 No Log 2 N n-cube Log 2 N Log 2 N nn/2 Yes Log 2 N 2D-mesh 4 2(n-1) 2(N-n) No N K-ary n-cube 2n N/ k/2 n x N Yes k x log 2 N

30 2.6 Summary Different topologies used for interconnecting multiprocessors were discussed. Taxonomy for interconnection networks based on their topology is introduced. Dynamic and static interconnection schemes have been studied. A number of basic performance aspects related to both dynamic and static interconnection networks have been introduced.

Interconnection Networks

Advanced Computer Architecture (0630561) Lecture 15 Interconnection Networks Prof. Kasim M. Al-Aubidy Computer Eng. Dept. Interconnection Networks: Multiprocessors INs can be classified based on: 1. Mode