chap7 managing memory

8/2/2019 Chap7 Managing Memory

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1A+ Guide to Managing and Maintaining Your PC, Fifth Edition

Understand @ Managing Memory

The term memory applies to any electronic

component capable of temporarily storing

data.There are two main categories of

memories which are internal memory and

auxiliary memory.

Internal Memory is memory that temporarilymemories. Uses by micro conductors, i.e fast

specialized electronic circuits.


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Understand @ managing memory(continue)

Auxiliary memory is memory that stores

information over the long term such as hard drive,

optical storage devices, cd-rom, dvd-rom and

others.



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RAM on the Motherboard

Loses all data when PC is turned off (except

data stored on CMOS chip)

Two categories Static RAM (SRAM)

Fast

Used as a memory cache

Dynamic RAM (DRAM)

Slower; requires constant refreshing


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DRAM


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SRAM


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Memory Technologies


7/497A+ Guide to Managing and Maintaining Your PC, Fifth Edition

How SRAM Is Used in DifferentMemory Caches



How Memory Caching Works



Dynamic RAM Technologies

Stored on DIMM, RIMM, or SIMM modules

(plug directly into motherboard)

Differences among these modules:

Width of data path that each type accommodates

The way data moves from system bus to module



Examples of Memory Modules



DRAM Technologies



DRAM Technologies (continued)


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DRAM

SIMM technologies

Can use either EDO or FPM technology

DIMM technologies

Can use either BEDO (burst EDO) or synchronous

RAM (SDRAM)

RIMM technologies

Each socket must be filled to maintain continuity


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Identifying the DIMM Module


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RIMM Technologies


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Error Checking and Parity

Parity Error-checking procedure in which every byte has

an even number of ones or an odd number of ones

Older method of testing integrity of bits Stored in RAM or secondary medium

Sent over a communications device

Error-correcting code (ECC)

Current method of error checking that can detect

and correct an error in a single bit


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Parity


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Other Memory Features

CAS (column access strobe) latency

RAS (row access strobe) latency

Both CAS and RAS refer to the number of

clock cycles it takes to write or read a column

or row of data


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Memory Speeds: Factors toConsider

Speed of memory in ns, MHz, or PC rating

How much memory is installed

Memory technology used

CL rating

ECC/parity or non-ECC/nonparity


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Factors That Contribute toMemory Speed


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Upgrading Memory

What to look for when buying memory chips

and modules

How much and what kind of memory to buy

Reading ads about memory modules

Installing memory


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What to Look for When BuyingMemory Chips and Modules

Use type, size, density, and fastest speed

supported by the motherboard

Match tin leads to tin connectors and gold

leads to gold connectors

Beware of remanufactured and re-marked

memory chips


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How Much and What Kind ofMemory to Buy Determine how much memory you have and

need

Identify the number, type, and size of memorymodules supported by your motherboard

Determine how much memory can you afford

Match memory modules to the motherboard


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Using Motherboard Documentationto Select Memory


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Using Motherboard Documentationto Select Memory (continued)


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RDRAM Memory Configuration


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Installing Memory

Protect chips against static electricity

Usually modules pop into place easily and are

secured by spring catches on both ends


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Installing a SIMM Module


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Installing a DIMM Module


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Installing a DIMM Module(continued)


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Installing a RIMM Module


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Troubleshooting Memory

What to do if the computer does not recognize

new SIMMs, DIMMs, or RIMMs, or memory

error messages appear

Recurring errors during normal operations can

mean unreliable memory


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Windows Memory Management

Evolution of OS memory management

Windows 9x memory management

Windows NT/2000/XP memory management


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Evolution of OS MemoryManagement

DOS and Windows 9x

Complicated; must deal with conventional, upper,

and extended memory for backward compatibility

Windows NT/2000/NT

Eliminates complexity; memory is simply

memory; all memory addresses are used the sameway

Causes loss of backward compatibility


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Division of Memory Under DOSand Windows 9x


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Assignment of Windows 9xMemory Addresses


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How Memory Addresses AreUsed


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How Memory Addresses AreUsed (continued)


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Memory Management Evolution

Wi d 9 M


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Windows 9x MemoryManagement

Views and manages memory addresses as

DOS did

Runs in protected mode and uses virtual

memory; does a better job managing extended

memory than DOS

H Wi d 9 d DOS


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How Windows 9x and DOSManage Memory Addressing

Wi d 9 d DOS U ili i


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Windows 9x and DOS UtilitiesThat Manage Memory

Himem.sys

Device driver for all memory above 640K

Emm386.exe

Contains software that loads device drivers andother programs into upper memory


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Using Himem.sys


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Using Emm386.exe

C ti d U i U


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Creating and Using UpperMemory Blocks

H Wi d 9 M


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How Windows 9x ManagesVirtual Memory Automates virtual memory management

Stores virtual memory in swap file andmanages that memory for application

programs Controlled by the VMM (memory paging)

Symptoms of excessive memory paging

Very high CPU use Very slow system response

Constant hard drive use

Wi d NT/2000/XP M


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Windows NT/2000/XP MemoryManagement

H Wi d 2000/XP


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How Windows 2000/XPManages Virtual Memory Default size of paging file is set to 1.5 times

amount of RAM installed

Guidelines for managing paging files

Set initial and maximum size of file to same value Balance file size with disk space usage

Move paging file to a volume other than bootvolume

Remember that memory dumps cannot be capturedif the paging file is on a different physical diskfrom the OS


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Summary

Memory

Required in order for a system to work

Stored on microchips, which are often stored on

memory modules (SIMMs, DIMMS, RIMMs)

Adding more memory can improve system

performance

How DOS, Windows 9x, and Windows

NT/2000/XP manage memory

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