L22 - Input and Output Devices ECS 154B Computer...

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1 ECS 154B Computer Architecture II Winter 2008 Disks 8.1-8.2 Adapted from slides by Mary Jane Irwin, Penn State 2 Input and Output Devices • I/O devices are incredibly diverse with respect to – Behavior – input, output or storage – Partner – human or machine – Data rate – the peak rate at which data can be transferred between the I/O device and the main memory or processor 240.0000-2560.0000 machine storage Magnetic disk 100.0000-1000.0000 machine input or output Network/LAN 800.0000-8000.0000 human output Graphics display 3.2000 human output Laser printer 0.0038 human input Mouse 0.0001 human input Keyboard Data rate (Mb/s) Partner Behavior Device 8 orders of magnitude range 3 I/O Performance Measures I/O bandwidth (throughput) – amount of information that can be input (output) and communicated across an interconnect (e.g., a bus) to the processor/memory (I/O device) per unit time 1. How much data can the system move in a certain time? 2. How many I/O operations can we do per unit time? I/O response time (latency) – the total elapsed time to accomplish an input or output operation – An especially important performance metric in real-time systems • Many applications require both high throughput and short response times 4 A Typical I/O System Processor Cache Memory - I/O Bus Main Memory I/O Controller Disk I/O Controller I/O Controller Graphics Network Interrupts Disk
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2 5 Magnetic Disk Purpose – Long term, nonvolatile storage – Lowest level in the memory hierarchy • slow, large, inexpensive General structure – A rotating platter coated with a magnetic surface – A moveable read/write head to access the information on the disk Typical numbers – 1 to 4 (1 or 2 surface) platters per disk of 1” to 5.25” in diameter (3.5” dominate in 2004) – Rotational speeds of 5,400 to 15,000 RPM – 10,000 to 50,000 tracks per surface cylinder - all the tracks under the head at a given point on all surfaces – 100 to 500 sectors per track • the smallest unit that can be read/written (typically 512B) Track Sector 6 Magnetic Disk Characteristic Disk read/write components 1. Seek time : position the head over the proper track (3 to 14 ms avg)
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This note was uploaded on 05/06/2008 for the course ECS 154b taught by Professor Krado during the Winter '08 term at UC Davis.

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L22 - Input and Output Devices ECS 154B Computer...

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