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Memory
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Section Objectives
After completing this section you will be able to: Differentiate between different memory technologies Plan for a memory installation or upgrade Install and remove memory chips Describe how memory works with the operating system Optimize memory for Windows-based platforms Troubleshoot memory problems
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Memory Overview
Types of Memory:
– RAM (Random Access Memory) is volatile memory found on the
motherboard and stores the operating system, the software applications,
and the data being used by all of the software.
– ROM (Read Only Memory) is a non-volatile type of memory that keeps
data in chips even when the computer is shut off.
Types of RAM:
– DRAM (Dynamic RAM) is less expensive, but slower than SRAM. It
requires periodic refreshing of the electrical charges holding the 1s and 0s.
– SRAM (Static RAM) is faster but more expensive than DRAM. It is also
known as cache memory or L2 cache.
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Memory Overview
Memory Terms:– Refreshing – Periodically rewriting information to the
memory chip.– Nanosecond – A billionth of a second.– Pipelining – The process by which microprocessors and
memory obtain computer software instructions in a timely fashion.
– Cache Memory – Can be found on the motherboard, but normally is found inside the CPU. Cache memory holds the most frequently used data so the CPU does not return to the slower DRAM chips to obtain the data.
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Memory Physical Packaging
Types of Memory Packaging:
– DIP (Dual In-line Package) – A chip that has a row of legs running
down each side.
– SIMM (Single In-line Memory Module) – Available in 30-pin and 72-
pin configurations.
– DIMM (Dual In-line Memory Module) – 168-pin, 184-pin and 240-pin
configurations.
– DDR DIMM – 184-pin configuration and single notch on bottom.
– RIMM – Type of memory module used on Pentium 4 computers.
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Memory Physical PackagingMemory chips
Memory – Figure 6.1
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Memory Physical Packaging184-Pin DDR DIMM and RIMM
Memory – Figure 6.2
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Planning the Memory Installation
Key points for planning a memory installation:– Refer to motherboard documentation to determine
what type of memory is supported– Determine what features are supported– Determine how much memory and how much of
each module is needed– Research prices– Purchase memory modules
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Planning the Memory Installation - Memory Chip Technologies
• Technology to provide faster DRAM speeds:– FPM (Fast Page Mode) – EDO (Extended Data Out) – BEDO (Burst EDO)
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Planning the Memory Installation – Memory Features
• Methods of Error Checking:
– Parity – A method for checking the accuracy of data going in or out of the memory chips.
– Non-parity – Memory chips that do not use any error checking.
– ECC (Error Correcting Code) – Uses a mathematical algorithm to detect up to four-bit memory errors and correct one-bit memory errors.
• A computer system that uses parity must have parity memory installed.
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Planning the Memory Installation – The Amount of Memory to Install
Memory is one of the easiest upgrades to increase computer performance.
Amount of memory needed depends on:Operating SystemTypes of applications usedHow many applications the user wishes to have
open at the same timeType of computerMaximum allowed by motherboard
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Common Memory Capacities:
DIMM Modules
256MB, 512MB, 1GB, 2GB, 4GB, and 8GB
RIMM Modules
64MB, 128MB, 256MB, and 512MB
Memory chips can have varying numbers: Example, 256 memory module showing 32Mx64
Planning the Memory Installation – The Amount of Memory to Install
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The starting point for memory is determined by your operating system.
The number of application the user wishes to run simultaneously and the application function also affect the amount of memory needed.
In Windows XP access the System Information window to determine the amount of memory you have.
It is necessary to take the cover off of the computer and look at the motherboard to determine the number of slots available.
Planning the Memory Installation – The Amount of Memory to Install
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Table 6.5
Common Computer Ports
Planning the Memory Installation – The Amount of Memory to Install
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Planning the Memory Installation – How Much of Each Memory Type
The motherboard manufacturer determines the number of memory slots, what type of memory modules fit in each slot, and the features the memory modules can have.
Single-sided memory – A memory module that the CPU accesses one at a time.
Double-sided memory – A memory module manufactured in a way that it has two memory modules in one container.
Dual-channel memory – The memory processing is handled more efficiently by the memory controller chip by handling two memory paths simultaneously.
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Planning for Memory – Research and Buy
Research and buying is one of the most confusing steps of memory installation/upgrade.
A confusing aspect of purchasing memory is memory speed which can be represented in nanoseconds, MHz, or the DDR PC Rating.
Access time – How fast information goes into a memory chip or is removed from the chip. (measured in nanoseconds)
CL rating (column address strobe (CAS) latency – The amount of time as measured in clock cycles that passes before the processor moves to the next memory address.
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Laptop Memory
Types of Laptop Memory:– SO-DIMM (Small Outline-DIMM) or
microDIMM – Special, smaller DIMM used in laptop computers.
– SO-RIMM (Small Outline-RIMM) – Special, smaller RIMM used in laptop computers.
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Installing Memory Overview
Installation Steps:– Determine which chip capacities can be used for the
system.– Determine how much memory is needed.– Determine what capacity chips go in each bank.
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Installing Memory Overview
Before removing or installing memory chips, always refer to the documentation for you computer.• Use an anti-static wrist strap when removing or
installing memory chips.
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Removing/Installing a DIP Chip
Some ROM chips and memory chips found on devices are socked DIP chips.
Use a DIP chip extractor to remove a DIP chip from a motherboard, but be careful not to bend the DIP chip legs.
A small flat screwdriver may also be used to remove DIP chips from a motherboard.
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Removing/Installing a DIP ChipDIP Chip Removal
Memory – Figure 6.9
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Removing/Installing a DIP Chip
To install a DIP chip, align the notch on the DIP chip with the notch on the motherboard. After ensuring that the legs are aligned with the socket, press down into place on the motherboard.
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Installing a DIP ChipDIP chip installation
Memory – Figure 6.10
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Removing/Installing a DIMM/RIMM
To remove a DIMM or a RIMM, push down on the outside edges of the DIMM’s retaining tabs. The DIMM/RIMM lifts slightly out of the socket.
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Removing/Installing a DIMM/RIMMDIMM/RIMM Removal
Memory – Figure 6.11
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Removing/Installing a DIMM/RIMM
To install a DIMM/RIMM, align the notches on the DIMM/RIMM with the socket and press down until the tabs close on the memory module.
DIMM/RIMM is inserted straight down into a socket. If the DIMM/RIMM does not insert easily, check the
notch for proper alignment.
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Adding More Cache/RAM
The motherboard manufacturer determines is any L3 cache can be installed.
Adding more RAM can make a noticeable difference in the performance of a computer. For today’s computer, it is recommended to have at least 128MB of RAM.
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Windows 9X/NT/2000/XP Disk Caching
Windows 98, NT, and 2000 have efficient memory management through the VMM (Virtual Memory Manager).
– Virtual Memory is a method of using the hard disk space as RAM.
– Swap File is a block of hard drive space used like RAM by applications.
– Pages – 4KB blocks of memory that the memory space is divided into
Steps to adjust the virtual memory swap file size can be found on page 183.
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Windows 9X/NT/2000/XP Disk Caching
Pages – 4kb blocks of memory, into which all memory space is divided
PAE (physical address extension) – PAE allows Windows XP systems to use up to 64GB of physical memory. The natural limit of Windows XP physical memory is 4GB.
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Monitoring Memory Usage Under Windows
Performance utility – Provided by Windows XP inside of the Task Manager to monitor memory usage.
Figure 6.14
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Old Applications Under NT Workstation/2000/XP
NTVDM (NT Virtual DOS Machine) – Allows the user to run 8-bit and 16-bit programs by simulating a 486 computer running DOS.
Many older applications will not run in the NT/2000/XP environments because they require direct calls to hardware.
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Troubleshooting Memory Problems
The following tips help with memory management:
– Add more RAM to help with performance.
– Adjust virtual memory size.
– Turn off the screen saver.
– Remove the desktop wallpaper scheme or use a very plain one.
– Put the swap file on the fastest hard drive.
– Do not put the swap file on multiple partitions that reside on the same hard drive.
– Put the swap file on a hard disk partition that does not contain the operating system.
– Adjust your Temporary Internet Files setting.
– Defragment the hard drive.
– Remove unnecessary files and applications from the hard drive.
– Empty the Recycle Bin.
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Flash Memory
Flash Memory is a type of non-volatile memory that holds data even when the computer power is off.– It is used with laptops because it is small, fast, and consumes little
power.– PCs use flash memory as a replacement for the BIOS chip.
CompactFlash (CF) – Is a small 50-pin removable storage device that allows speeds up to 16 MBps CF has two main standards, CompactFlash and CF+
SmartMedia – A trademark of the Toshiba Corporation and is used in a variety of devices such as cameras, PDAs, musical instruments, printers, faxes, MP3 players, and scanners. There are two versions of SmartMedia cards – 3.3V and 5V.
USB flash drives – Allows storage up to 8 GB with higher capacities expected.
