Understanding and Troubleshooting

Your PC

Chapter 4: Managing Memory 2

Chapter Objectives

In this chapter, you will learn:– About the different kinds of physical memory

(RAM) used on the motherboard– About Windows memory management– How to upgrade memory modules– How to troubleshoot memory

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RAM on the Motherboard

Memory is divided into two categories: ROM and RAM

ROM retains its data when the computer is turned off

RAM loses all of its data when the computer is turned off

A computer system has two kinds of memory

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RAM on the Motherboard

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Static RAM Technologies

Memory caching is a method used to store data or programs in SRAM for quick retrieval

Memory caching relies on SRAM chips to store data and a cache controller to manage the storage and retrieval of data from SRAM

When cache memory is located on the motherboard, it either is located on individual chips or on a memory module called cache on a stick

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Static RAM Technologies

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Static RAM Technologies

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Dynamic RAM Technologies

Dynamic RAM (DRAM) needs to be refreshed every few milliseconds

DRAM is refreshed by the memory controller

In current PCs, DRAM is always stored in DIMM, RIMM, or SIMM modules, which plug directly into a bank on the mother board

A bank is a location on the motherboard that contains slots for memory modules

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Dynamic RAM Technologies

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SIMM Technologies

SIMMs are rated by speed, measured in nanoseconds

This speed is a measure of access timeCommon SIMM speeds are 60, 70, or 80 nsThe smaller the speed rating is, the faster the

chip

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DIMM Technologies

A DIMM is a memory module that has pins on opposite sides of the circuit board that do not connect and thus form two sets of contacts

Contain 168 or 184 pinsHold between 8 MB and 2 GB of RAMNewer DIMMS hold chips that use

synchronous DRAM (SDRAM), which is DRAM that runs in sync with the system clock and thus runs faster than other types of DRAM

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RIMM Technologies

A RIMM is a memory module that houses Rambus DRAM (RDRAM) chips, which are much faster than SDRAM

With RIMMs, each socket must be filled to maintain continuity throughout all sockets

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Factors Determining Memory Speeds

Speed of memoryMemory technology usedLatency ratingType of error checking usedSingle channel versus dual channel

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Factors Determining Memory Speeds

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Factors Determining Memory Speeds

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Windows Memory Management

The process of assigning memory address to programs is called memory mapping

Once memory addresses have been assigned, they can be used for communication with software

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The Evolution of OS Memory Management

Early CPUs only had 20 lines on the bus available to handle addresses, which was 1MB of memory, divided up as follows:

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The Evolution of OS Memory Management

If the OS is low on RAM, it can store some data on the hard drive, a method called virtual memory

Data transferred to virtual memory is stored in a file on the hard drive called a swap file or paging file

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The Evolution of OS Memory Management

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Memory Management in Windows NT, Windows 2000, Windows XP, and Windows Server 2003 With this model, an application or device driver

indicates that it needs memory, but it does not have to tell Windows which physical or which memory addresses it wants

Memory is allocated in 4K segments or pages Windows assigns a certain number of pages to an

application or device driver that needs memory Windows virtual memory manager handles managing

the memory addresses used for each page and can choose to store these pages in RAM or in the hard drive in the swap file named Pagefile.sys

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Memory Management in Windows NT, Windows 2000, Windows XP, and Windows Server 2003

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Upgrading Memory

Determine how much memory you have, and how much you need

Determine the size and type of modules you should buy to be compatible with the memory you already have installed

Determine how much and what types of memory you can fit on the motherboard

Determine how much you can afford

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Amount of Existing Memory and Additional Memory Needed

Right-click My Computer on the Start menu, click Properties, and then click the General tab to determine how much memory you have

If possible upgrade a Windows XP system to at least 512 MB of RAM

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Match Memory Modules to the Motherboard

Newer motherboards support either ECC or non-ECC memory

Check the motherboard documentation to determine what to install

Computers use one or two methods to detect memory– Parallel Presence Detect (PPD)– Serial Presence Detect (SPD)

Match the type of memory to the motherboard requirements

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Memory Types Supported by the Motherboard

Read the documentation for your motherboard to determine what memory speed or speeds to use on your board

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Memory Types Supported by the Motherboard

Types of memory modules used on motherboards:– 72-pin SIMMs– DIMMs

• 184-pin DDR SDRAM• 2.5V• Unbuffered• DDR400

– RIMM Modules

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Memory Types Supported by the Motherboard

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Purchasing Memory Modules

Before purchasing memory, check your motherboard documentation to determine if you need proprietary memory

Proprietary memory typically costs more than memory purchased from a third-party company

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Reading Ads for Memory Modules

Advertisements typically include information about the speed, the size, the type of module, and more

For DIMMS, the add might list the density of the module, which is written as two numbers separated by x

Density allows you to determine three important things about the memory module:– Width of the data bus– ECC or non-ECC– Module size

For Rambus memory, ads list the module size in MB

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Reading Ads for Memory Modules

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Determining the Quality of Memory Modules

Poor-quality memory chips can cause frequent application errors, errors that cause the system to freeze, and General Protection Fault (GPF) errors

Consider the following when shopping for memory chips:– Tin or Gold Leads– Remanufactured and Used Modules– Re-Marked Chips

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Installing Memory

Protect the chips against static electricityAlways use a ground bracelet as you workBe sure you have written down CMOS

settings, and make a recovery disk if you do not already have one

Turn off the computer and unplug it before you remove the cover

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Installing Memory

Installing a SIMM module

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Installing Memory

Installing a DIMM module

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Installing Memory

After you placed each module securely in its slot, turn on your PC and watch POST count the amount of memory during the boot process, if possible

Check the total memory on the system in the System Properties window to make sure it reads all memory you have installed

Update your records with the new memory configuration in your computer

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Troubleshooting Memory

Check that you have installed memory modules that are supported by your motherboard

Check that you have installed the right module size, as stated in the motherboard documentation

Remove and reinstall each module. Confirm that the memory modules are properly seated, and that each module sits in the socket at the same height as other modules

Remove the newly installed memory, place the memory in different sockets or slots, and check whether the error message disappears

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Troubleshooting Memory

Try installing the new memory without the old installed. If the new memory works without the old, then the new and old modules are not compatible

Clean the module edge connectors with a soft cloth or contact cleaner. Blow or vacuum dust from the memory sockets

Try flashing your BIOS, using the steps outlined in Chapter 3. It is possible the BIOS has problems with the new memory that a BIOS upgrade can solve

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Troubleshooting Memory

If you have recurring errors and have not just upgraded the memory, try the following:– Run a current version of antivirus software to check for viruses– The problem might be with the OS or applications. Download the latest

patches for your operating system and application software from the manufacturers’ Web sites

– If you have just installed new hardware, the hardware device might be causing an error, which the OS interprets as a memory error. Try uninstalling the new hardware

– A Windows error that occurs randomly and generates an error message with exception fault 0E at >>0137:BFF9z5d0 or similar text is probably a memory error. Test, reseat, or replace RAM

– Sometimes a problem can result from a bad socket or a broken trace (a fine printed wire or circuit) on the motherboard. Check the motherboard for visible problems. If you find an issue, you might have to replace the entire motherboard

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Chapter Summary

In this chapter, you learned:– About the different kinds of physical memory

(RAM) used on the motherboard– About Windows memory management– How to upgrade memory modules– How to troubleshoot memory

Understanding and Troubleshooting

Your PCChapter 4 Complete