Lecture5nFull - Click to edit Master subtitle style Lecture...

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Unformatted text preview: Click to edit Master subtitle style 8/1/11 Lecture 5 COT 4600 Operating Systems Spring 2011 Dan C. Marinescu Office: HEC 304 Office hours: Tu-Th 6:00-7:15 PM Lecture 5 8/1/11 n Last time: ¨ Discussion of the paper “Architecture of Complexity” by H. A. Simon ¨ Modularity, Abstractions, Layering, Hierarchy n Today: n Discussion of the paper “Hints for Computer Systems Design” by Butler Lampson. n Layering and Hierarchy for Coping with Complexity n Complexity of Computer Systems n Bandwidth and Latency n Iteration n Names and The Basic Abstractions n Memory. Critical Properties of Memory Systems. ¨ Read-Write Coherence ¨ Before or After Atomicity n Next time ¨ Raid Systems Lecture 5 – Thursday, January 27 2011 Lecture 5 Lecture 5 8/1/11 Layering for Coping with Complexity n Layering h building a set of successive functional entities with restricted communication patterns, a layer may only communicate with the layer below it and with the one above it. n Examples: networking Lecture 5 8/1/11 Hierarchy for Coping with Complexity n Hierarchical structures & construct a large system from a small collection of relatively large subsystems n Examples: ¨ Corporations ¨ An army ¨ A computer is a collection of subsystems Lecture 5 8/1/11 Names n Modularity along with abstraction, layering, and hierarchy allow a designer to cope with complexity; n Names and addresses “ provide the means to connect modules. n A system O a bunch of resources, glued together with names n Naming allows the designer to: ¨ Delay the implementation of some modules; use dummy ones ¨ Replace an implementation with another one. n Binding& choosing an implementation for a module ¨ Delayed binding; use a place holder. Lecture 5 8/1/11 Digital computers - a distinct species of complex systems n The complexity of digital computer systems not limited by the laws of physics & distant bounds on composition ¨ Digital systems are noise-free. ¨ The hardware is controlled by software n The rate of change unprecedented ¨ The cost of digital hardware has dropped in average 30% per year for the past 35 years Lecture 5 Lecture 5 8/1/11 Analog, digital, and hybrid systems n Analog systems: ¨ the noise from individual components accumulate and ¨ the number of components is limited n Digital systems: ¨ are noise-free ¨ the number of components is not limited ¨ regeneration & restoration of digital signal levels ¨ static discipline& the range of the analog values a device...
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Lecture5nFull - Click to edit Master subtitle style Lecture...

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