Five Classic Components of a Computer - UCLA Computer Science五个经典的计算机组件-加州大学洛杉矶分校的计算机科学.ppt

Five Classic Components of a Computer Current Topic: Input and Output What You Will Learn in This Set of Lectures I/O System Overview I/O System Design Considerations I/O System Design Parameters Connectivtiy Protocol Access Control Performance Expandability Failure Handling Operating System Support I/O Implementation Example Who Cares About I/O? CPU Performance: 60% per year I/O system performance limited by mechanical delays (disk I/O) 10% per year (IO per sec or MB per sec) Amdahls Law: system speed-up limited by the slowest part! 10% IO 10x CPU ? 5x Performance (lose 50%) 10% IO 100x CPU ? 10x Performance (lose 90%) I/O bottleneck: Diminishing fraction of time in CPU Diminishing value of faster CPUs I/O System Architecture Overview How is the I/O System Related to Processor A Classificaiton of I/O According to the Targets of I/O Operation Processor to Memory Very low latency, very high throughput, very low protocol overhead Processor to Peripheral Latency, throughput, and protocol overhead vary according to the I/O devices Processor to Processors Tightly Coupled: all processors share a physical memory Low latency, high throughput, low overhead protocol, coherence problem Loosely Coupled: each processor has its own physical memory Medium latency, medium throughput, high protocol overhead, scalable Processor to Network High latency, low throughput, high protocol overhead, very scalable I/O System Example I/O Devices Examples Device Behavior Partner Data Rate (KB/sec) Keyboard Input Human 0.01 Mouse Input Human 0.02 Line Printer Output Human 1.00 Floppy disk Storage Machine 50.00 Laser Printer Output Human 100.00 Optical Disk Storage Machine 500.00 Magnetic Disk Storage Machine 5,000.00 Network-LAN Input/Output Machine 20 – 1,000.00 Graphics Display Output Human 30,000.00 See Backup Slides for More Detailed Information about Some of the I/O Devices I/O System Design Process Esta