Computer Architecture

Computer Architecture - 1 ENG SC757 - Advanced...

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Unformatted text preview: 1 ENG SC757 - Advanced Microprocessor Design Babak Kia Adjunct Professor Boston University College of Engineering Email: bkia -at- bu.edu Computer Architecture Computer Architecture z Computer Architecture is the theory behind the operational design of a computer system z This is a term which is applied to a vast array of computer disciplines ranging from low level instruction set and logic design, to higher level aspects of a computers design such as the memory subsystem and bus structure z In this lecture we will focus on the latter definition of the term Topics Discussed z Memory Hierarchy z Memory Performance Amdahls Law and the Locality of Reference z Cache Organization and Operation z Random Access Memory (DRAM, SRAM) z Non Volatile Memory (Flash) z Bus Interfaces How to connect the processor to memory & I/O 2 Memory Hierarchy z A simple axiom of hardware design: smaller is faster 1000+ cy. Disk 10-15 cy. Main Memory 1-2 cy. Cache 1 cy. Register Access Times Memory Hierarchy Memory Performance z Performance is measured either in terms of throughput or response time z The goal of memory design is to increase memory bandwidth and decrease access time latencies z We take advantage of three principles of computing in order to achieve this goal: Make the common case faster Principle of Locality Smaller is Faster Make the Common Case Faster z Always want to improve the frequent event as opposed to the infrequent event z Amdahls Law quantifies this process: The performance improvement to be gained from using some faster mode of execution is limited by the fraction of the time the faster mode can be used z Amdahls Law essentially guides you to spend your resources on an area where the time is most spent 3 The Principle of Locality z Locality of Reference is one of the most important properties of a program: It is a widely held rule of thumb that 90% of execution time is spent in only 10% of the code z Temporal Locality If a location is referenced, there is a high likelihood that it will be referenced again in the near future (time) z Spatial Locality If you reference instruction or data at a certain location, there is a high likelihood that nearby addresses will also be referenced Cache z Cache is a small, fast memory which holds copies of recently accessed instruction and data z Key to the performance of modern Microprocessors z There could be up to two levels of cache, the picture to the right is Intel Pentium M, the large block to the left showing 2 MB of L2 cache Cache z Taking advantage of the Principle of Locality, cache loads itself with contents of data which was recently accessed z But this only addresses temporal locality!...
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This note was uploaded on 02/09/2012 for the course CSCI 504 taught by Professor Jon during the Spring '11 term at IUP.

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Computer Architecture - 1 ENG SC757 - Advanced...

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