WVU CPE 242 - Interconnection Networks (32 pages)

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Interconnection Networks



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Interconnection Networks

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Pages:
32
School:
West Virginia University
Course:
Cpe 242 -
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CpE 242 Computer Architecture and Engineering Interconnection Networks cs 152 nets 1 DAP SIK 1995 Recap Advantages of Buses Processor I O Device I O Device I O Device Memory Versatility New devices can be added easily Peripherals can be moved between computer systems that use the same bus standard Low Cost A single set of wires is shared in multiple ways cs 152 nets 2 DAP SIK 1995 Recap Disadvantages of Buses Processor I O Device I O Device I O Device Memory It creates a communication bottleneck The bandwidth of that bus can limit the maximum I O throughput The maximum bus speed is largely limited by The length of the bus The number of devices on the bus The need to support a range of devices with cs 152 nets 3 Widely varying latencies Widely varying data transfer rates DAP SIK 1995 Recap Types of Buses Processor Memory Bus design specific Short and high speed Only need to match the memory system Maximize memory to processor bandwidth Connects directly to the processor I O Bus industry standard Usually is lengthy and slower Need to match a wide range of I O devices Connects to the processor memory bus or backplane bus Backplane Bus industry standard Backplane an interconnection structure within the chassis Allow processors memory and I O devices to coexist Cost advantage one single bus for all components cs 152 nets 4 DAP SIK 1995 Recap Increasing the Bus Bandwidth Separate versus multiplexed address and data lines Address and data can be transmitted in one bus cycle if separate address and data lines are available Cost a more bus lines b increased complexity Data bus width By increasing the width of the data bus transfers of multiple words require fewer bus cycles Example SPARCstation 20 s memory bus is 128 bit wide Cost more bus lines Block transfers Allow the bus to transfer multiple words in back to back bus cycles Only one address needs to be sent at the beginning The bus is not released until the last word is transferred Cost a increased complexity b decreased response time for request cs 152 nets 5 DAP SIK 1995 Bus Summary Bus arbitration schemes Daisy chain arbitration it cannot assure fairness Centralized parallel arbitration requires a central arbiter I O device notifying the operating system Polling it can waste a lot of processor time I O interrupt similar to exception except it is asynchronous Delegating I O responsibility from the CPU Direct memory access DMA I O processor IOP cs 152 nets 6 DAP SIK 1995 Outline of Today s Lecture Recap and Introduction 5 minutes Introduction to Buses 15 minutes Bus Types and Bus Operation 10 minutes Bus Arbitration and How to Design a Bus Arbiter 15 minutes Operating System s Role 15 minutes Delegating I O Responsibility from the CPU 5 minutes Summary 5 minutes cs 152 nets 7 DAP SIK 1995 Networks Goal Communication between computers Eventual Goal treat collection of computers as if one big computer Theme Different computers must agree on many things Overriding importance of standards Warning Buzzword rich environment cs 152 nets 8 DAP SIK 1995 Current Major Networks IP internet Protocol TCP Transmission Control Protocol CS Net FDDI 100Mbps Phonenet T1 56Kbps ARPA net NSF Net CS Net Relay 1 6Mbps 10 Mbps Token Ring 4Mbps Ethernet cs 152 nets 9 T3 230Kbps Bitnet ATM X 25 Telenet Uninet DAP SIK 1995 Networks Facets people talk a lot about direct vs indirect topology routing algorithm switching wiring What matters latency bandwidth cost reliability cs 152 nets 10 DAP SIK 1995 ABCs of Networks Starting Point Send bits between 2 computers FIFO Queue on each end Can send both ways Full Duplex Rules for communication protocol Inside a computer Loads Stores Request Address Response Data Need Request Response Name for standard group of bits sent Packet cs 152 nets 11 DAP SIK 1995 A Simple Example What is format of packet Fixed Number bytes Request Response Address Data 1 bit 32 bits 0 Please send data from Address 1 Data corresponding to request cs 152 nets 12 DAP SIK 1995 Questions about Simple Example What if more than 2 computers want to communicate Need computer address field in packet What if packet is garbled in transit Add error detection field in packet What if packet is lost More elaborate protocols to detect loss What if multiple processes machine Queue per process Questions such as these lead to more complex protocols and packet formats cs 152 nets 13 DAP SIK 1995 Protocol Stacks OSI Reference Model Virtual terminal Application File transfer Application interface Presentation Frequently used functions e g char conversion Presentation Session Session Manage dialogue Synchronization TCP Transport IP Network Network Network Network Data link Data link Data link Data link Framing Error recovery Physical Physical Physical Physical Xmit raw bits M edium Access Host A cs 152 nets 14 Transport Subnet Routing Flow control Congestion Host B DAP SIK 1995 Interconnection Networks Examples MPP networks CM 5 1000s nodes 25 meters per link Local Area Networks Ethernet 100s nodes 1000 meters Wide Area Network ATM 1000s nodes 5 000 000 meters cs 152 nets 15 DAP SIK 1995 Interconnection Network Issues Implementation Issues Performance Measures Architectural Issues Practical Issues cs 152 nets 16 DAP SIK 1995 Implementation Issues Interconnect MPP LAN WAN Example CM 5 Ethernet ATM Maximum length between nodes 25 m 500 m 5 repeaters copper 100 m optical 1000 m Number data lines 4 1 1 Clock Rate 40 MHz 10 MHz 155 5 MHz Shared vs Switch Switch Shared Switch Maximum number 2048 254 10 000of nodes Media Material wire fiber Copper Twisted pair copper wire or cable cs 152 nets 17 Twisted pair or Coaxial copper optical DAP SIK 1995 Medi Tawisted Pair Several Mb s up to km more with shielded twisted pair category 5 4 wires Why twisted Coaxial Cable Plastic Covering Braided outer conductor Insulator Copper core Fiber Optics Transmitter L E D Laser Diode Air light source 10Mbps at 1km more at shorter length Tap with T junction or vampire Total internal reflection Silica Multimode many rays bouncing at different angles Single mode diameter of fiber less than one wavelength acts like a wave guide Line of sight microwave cs 152 nets 18 Receiver Photodiode Gb s at 1 km 2 40 GHz DAP SIK 1995 Implementation Issues Advantages of Serial vs Parallel lines No synchronizing signals Higher clock rate and longer distance than parallel lines e g 60 MHz x 256 bits x 0 5 m vs 155 MHz x 1 bit x 100 m Imperfections in the copper wires or integrated circuit pad drivers can


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