17-Advanced Bus Concepts

17-Advanced Bus Concepts - Advanced Bus Concepts Presenter...

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Tathagata Bhattacharjee 1 Advanced Bus Concepts Presenter Tathagata Bhattacharjee
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What is a bus? Tathagata Bhattacharjee 2 A Bus Is: shared communication link single set of wires used to connect multiple subsystems A Bus is also a fundamental tool for composing large, complex systems systematic means of abstraction Control Datapath Memory Processor Input Output
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Busses Tathagata Bhattacharjee 3
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Advantages of Buses Memory Processor I/O Device I/O Device I/O Device Tathagata Bhattacharjee 4 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
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Disadvantage of Buses Tathagata Bhattacharjee 5 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: » Widely varying latencies » Widely varying data transfer rates Memory Processor I/O Device I/O Device I/O Device
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General Organization of a Bus Data Lines Control Lines Tathagata Bhattacharjee 6 Control lines : Signal requests and acknowledgments Indicate what type of information is on the data lines Data lines carry information between the source and the destination: Data and Addresses Complex commands
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Master versus Slave Bus Master Bus Slave Master issues command Data can go either way Tathagata Bhattacharjee 7 A bus transaction includes two parts: Issuing the command (and address) – request Transferring the data – action Master is the one who starts the bus transaction by: issuing the command (and address) Slave is the one who responds to the address by: Sending data to the master if the master ask for data Receiving data from the master if the master wants to send data
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Types of Busses Tathagata Bhattacharjee 8 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 Optimized for cache block transfers 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 (standard or proprietary) Backplane: an interconnection structure within the chassis Allow processors, memory, and I/O devices to coexist Cost advantage: one bus for all components
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Example: Pentium System Organization Tathagata Bhattacharjee 9 Processor/Memory Bus PCI Bus I/O Busses
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A Computer System with One Bus Processor Memory I/O Devices Backplane Bus Tathagata Bhattacharjee 10 A single bus (the backplane bus) is used for: Processor to memory communication Communication between I/O devices and memory Advantages: Simple and low cost Disadvantages: slow and the bus can become a major bottleneck Example: IBM PC - AT
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This note was uploaded on 07/15/2011 for the course ECO 2023 taught by Professor Mr.raza during the Summer '10 term at FAU.

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17-Advanced Bus Concepts - Advanced Bus Concepts Presenter...

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