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Chapter Overview

ROM and RAM Memory Mapping

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Defining Memory

Memory is the area within a computer where information is stored while being worked on. Information is stored by using 0s and 1s as

switches. When strung together, these switches can

represent large numbers and code values.

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Nonvolatile and Volatile Memory

Computer memory includes two major classes. Nonvolatile: computer retains data when

the power is shut off Volatile: computer loses data when the

power is shut off

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Read-Only Memory (ROM) Is nonvolatile memory, generally

installed during manufacturing Protects the information required to

start and run the computer Holds instructions for performing the

power-on self test (POST) and basic input/output system (BIOS) information

Requires attention only if it needs to be replaced or upgraded

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Random Access Memory (RAM)

Is volatile memory Includes two common forms

Dynamic RAM (DRAM) Synchronous DRAM (SDRAM)

Uses two methods to ensure data integrity Parity Error-correction encoding (ECC)

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RAM Packaging

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Memory Configuration

8-bit data bus requires memory in 8-bit chunks.

16-bit data bus requires memory in 16-bit chunks.

32-bit data bus requires memory in 32-bit chunks.

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Installing SIMMs

Check the memory module voltage. Use electrostatic discharge (ESD)

protection and handle single inline memory modules (SIMMs) carefully.

Insert the SIMM at a 45-degree angle and click it into place. (The notch in the SIMM prevents improper installation.)

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Cache Memory

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Hexadecimal Code

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Memory Allocation

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Shadow RAM

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Determining Usable Memory

MEM.COM DisplayMEM.COM Display

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Chapter Summary The two basic computer memory types are

ROM (nonvolatile) and RAM (volatile). RAM is packaged in a variety of designs. Installing SIMMs requires ESD protection

and careful handling. Cache memory enhances performance. Hexadecimal code simplifies binary code

notation. Memory allocation has been simplified

under Microsoft Windows.