21524359-Computer-Organization-Articture-No-9-from-APCOMS

21524359-Computer-Organization-Articture-No-9-from-APCOMS -...

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COA by Athar Mohsin Lecture 09 Memory interleaving
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COA by Athar Mohsin Main Memory The basic unit of memory is the binary digit “ bit ”. A bit contains a “0” or “1”. The most common definition of the word length of a computer is the number of bits actually stored or retrieved in one memory access. Word length and address length are independent. Up to 2 k  addressable MDR MAR Connection of the memory to the processor. k -bit address bus n -bit data bus Control lines (          , MFC, etc.) Processor  Memory locations Word length = n  bits W R /
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COA by Athar Mohsin Types of Memory Unit Random-Access Memory (RAM) Static RAM (SRAM) Memories that consist of circuits capable of retaining their state as long as power is applied. SRAMs are fast (a few nanoseconds access time) but their cost is high. Dynamic RAM (DRAM) • These memory units are capable of storing information for only tens of milliseconds, thus require periodical refresh to maintain the contents.
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COA by Athar Mohsin Types of Memory Unit Read-Only Memory (ROM) Nonvolatile memory Data are written into a ROM when it is manufactured. Normal operation involves only reading of stored data. ROM are useful as control store component in a micro- programmed CPU (micro-coded CPU). ROM is also commonly used for storing the bootstrap loader , a program whose function is to load the boot program from the disk into the memory when the power is turn on.
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COA by Athar Mohsin Types of Memory Unit PROM (Programmable ROM) data is allowed to be loaded by user but this process is irreversible provide a faster and less expensive approach when only a small number of data are required EPROM (Erasable, reProgrammable ROM) stored data can be erased by exposing the chip to ultraviolet light and new data to be loaded EEPROM stored data can be erased electrically and selectively different voltages are needed for erasing, writing, and reading the stored data
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COA by Athar Mohsin Types of Memory Unit Flash memory similar to EEPROM technology it is possible to read the contents of a single cell, but it is only possible to write an entire block of cells
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This note was uploaded on 01/06/2010 for the course CS it666 taught by Professor Tony during the Spring '06 term at 東京大学.

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21524359-Computer-Organization-Articture-No-9-from-APCOMS -...

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