05 - Lecture 05 - 05/12/2010 Computer Organization and...

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1 Computer Organization and Architecture Cache Memory, Internal Memory External Memory Dr. Ersun İşçioğlu Eastern Mediterranean University, School of Computing and Technology, Department of IT e-mail: ersun.iscioglu@emu.edu.tr General Characteristic of Memory Systems a. Location b. Capacity c. Unit of transfer d. Access method e. Performance f. Physical type g. Physical characteristics h. Organization -2-
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2 General Characteristic of Memory System… a. Location Processor Internal: main memory, registers, caches External: disk, tape (accessible via I/O controller) b. Capacity Word size: no of bits used to represent a number no of addressable units Capacity expressed in bytes (words)1 byte=8 bits For addresses of length A (in bits), no if addressable units is 2 A common word lengths 8,16,32 bits -3- no of bits General Characteristic of Memory System… b Unit of transfer h Word h Block h For internal memory: no of data lines into and out of memory module (64, 128, 256,bits or a word 8 bits) h For main memory: no of bits readout or written into memory at a time h For external memory: data transferred much larger units B blocks -4-
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3 General Characteristic of Memory System… b Access method c Sequential c Direct c Random c Associative -5- General Characteristic of Memory System… b Access method h Sequential x Memory is organized into units of data B records x Access starts at beginning and read in order x Access time depends on location of data x Tape units are sequential access h Direct x Individual blocks or records have unique address based on physical location x Access is direct access to desired information x Access time depends on location of data x Disk unit are direct access -6-
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4 General Characteristic of Memory System… b Access method (Continue) h Random x Access is direct to desired location x Access time is constant x Main memory & some cache systems are random access h Associative x Data is located by comparison with contents of a portion of store x Access time is constant x Cache memories may employ associative access -7- General Characteristic of Memory System… b Performance s Access time (Latency) x For random access: time taken to perform a read or write operation x For non-random access: time taken to position read\write mechanism at desired location s Memory cycle time (MCT) s Time to recover before next access s Related with system bus, not processor s Transfer rate s Rate at which data can be transferred into or out of a memory unit (bits/second) -8-
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5 General Characteristic of Memory System… b Physical type: most common are semiconductor (RAM) and magnetic surface memories (disk, tape) and optical (CD, DVD) B Semiconductor B Magnetic B Optical B Magnetic optical b Physical characteristics h Volatile: information is lost when power is switched off h Non-volatile: information remains without deterioration until changed h Non-erasable: can’t be altered except by destroying storage unit (ROM) h Erasable b Organization -9- Computer Memory Hierarchy b
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This note was uploaded on 08/12/2011 for the course ITEC 255 taught by Professor Ersuniscioglu during the Spring '11 term at Eastern Mediterranean University.

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05 - Lecture 05 - 05/12/2010 Computer Organization and...

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