Memory Organization ch4.ppt - Chapter four Memory Organization 1 Outline Introduction Computer Memory System Overview Characteristics of Memory Systems

Memory Organization ch4.ppt - Chapter four Memory...

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Chapter four Memory Organization 1
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Outline Introduction Computer Memory System Overview Characteristics of Memory Systems The Memory Hierarchy Cache Memory Principles Elements of Cache Design 2
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Introduction computer memory exhibits perhaps the widest range of type technology organization performance and cost of any feature of a computer system. No one technology is optimal in satisfying the memory requirements for a computer system. 3
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Introduction As a consequence, the typical computer system is equipped with a hierarchy of memory subsystems, some internal to the system (directly accessible by the processor) and some external (accessible by the processor via an I/O module 4
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MEMORY SYSTEM OVERVIEW Characteristics of Memory Systems The Memory Hierarchy 5
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Characteristics of Memory Systems 6
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Location Internal External: accessible to the processor via I/O controllers Disk and tape Capacity Internal: byte or word External: byte 7
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unit of transfer Internal: the number of electrical lines into and out of the memory module External : data are often transferred in much larger units than a word, and these are referred to as blocks Word: the number of bits used to represent an integer and to the instruction length Unit of transfer: the number of bits read out of or written into memory at a time 8
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method of accessing Sequential access: a specific linear sequence. Stored addressing information is used to separate records and assist in the retrieval process A shared read–write mechanism is used moved from its current location to the desired location, passing and rejecting each intermediate record access time is variable Example: Tape 9
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Direct access: Shared read–write mechanism Individual blocks or records have a unique address based on physical location. Access is by Sequential searching, counting, or waiting to reach the final location access time is variable Example: Disk 10
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Random access : each data unit has a unique, physically wired-in addressing mechanism The time to access a given location is independent of the sequence of prior accesses and is constant any location can be selected at random and directly addressed and accessed Example: RAM, some cache memories 11
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Associative: similar to random access Making a comparison of desired bit locations within a word for a specified match a word is retrieved based on a portion of its contents rather than its address retrieval time is constant E.g. Cache memories 12
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Access time (latency) Random-access time it takes to perform a read or write operation
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  • Fall '19
  • Central processing unit, CPU cache

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