Memory
Chapter 6
Objectives
After completing this chapter 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
Memory Overview
• The two main types of memory are RAM (random
access memory) and ROM (read only memory).
• RAM is volatile memory; the information in RAM
is lost when you power off the computer. ROM is
nonvolatile memory; the information is in ROM
even when the computer is powered off.
• RAM is divided into two major types: DRAM
(dynamic RAM) and SRAM (static RAM). DRAM is
less expensive, but slower than SRAM.
• SRAM is also known as cache memory.
Memory Physical Packaging
• A DIP (Dual In-line Package) chip has a row of legs
running down each side. The oldest motherboards
use DIP chips for the DRAM.
• SIMMs (Single In-line Memory Modules) came
along next. Two types of SIMMs were used: 30-pin
and 72-pin.
• The memory chip used today is a DIMM (Dual Inline Memory Module), which has 168, 184, or 240
pins.
• Figure 6.1 shows the progression of memory
packaging.
Planning the Memory Installation
Some key points to discuss follow:
• Refer to the system or motherboard
documentation to see what type of memory is
supported
• Determine what features are supported
• Determine how much memory is needed
• Determine how many of each memory module is
needed
• Research prices and purchase memory
module(s)
Planning the Memory Installation—
Memory Technologies
• Technology has provided faster DRAM speeds
without increasing the cost too greatly.
• These DRAM technologies include FPM (fast page
mode) RAM, EDO (extended data out) RAM, BEDO
• (burst EDO) RAM, SDRAM (synchronous DRAM),
DDR RAM, and RDRAM (Rambus DRAM).
• The motherboard must be designed to use one of
these technologies or the faster memory will not
speed up the computer.
• Table 6.1 explains some of the memory technologies.
• Most people cannot tell the difference between a
DDR, DDR2, or DDR3 memory module.
• Even though DDR uses 184 pins and DDR2 uses 240
pins, they are the same physical size.
• DDR3 modules also have 240 pins but will not fit in
a DDR2 slot.
• Figure 6.3 shows DDR2 and DDR3 DIMMs and
Table 6.2 lists many of the DIMM models.
Planning the Memory Installation—
Memory Features
• In addition to having to determine what type of
memory chips are going to be used, you must
determine what features the memory chip might
have.
• The computer system or motherboard
documentation is going to delineate what
features are supported.
• Table 6.3 helps characterize memory features.
Planning for Memory—
The Amount of Memory to Install
• Memory chips are sometimes shown with varying
numbers.
▫ For example, a chip may be shown as 32Mx64 and actually
be a 256MB memory module.
▫ The 32Mx64 is describing the memory chip in more detail—
there are 32 million locations with 64 bits in each location.
▫ 32 million times 64 is the chips capacity in megabits. Divide
by 8 and you get the chips capacity in megabytes.
▫ When parity is used with DIMMs, you see the second
number as 72; for example, 32Mx72 is still 256MB. Those
extra 8 bits are used for error checking.
• Table 6.4 shows sample memory configurations.
• The operating system you use determines to a great
extent the starting point for the amount of memory
to have.
• Table 6.5 is the starting point for calculating
memory requirements.
▫ Remember that as you want to run more applications
simultaneously and the higher the application
function, the more memory you will need.
• If upgrading memory, you need to know a couple of
key pieces of information.
▫ How much memory you are starting with?
▫ How many motherboard RAM slots are currently
being used and whether you have any slots free?
▫ What is the maximum amount of memory that your
motherboard supports?
• To determine how much memory you have,
access the System Information window (right
click My Computer or Computer → Properties)
or from the Run prompt, type MSINFO32 and
press enter. Scroll down to see the memory
information.
• Figure 6.4 shows how a computer system
currently has 1GB of RAM installed
(1,024.00MB total physical memory).
Planning for Memory—
How Many of Each Memory Type?
• A motherboard has a certain number of memory slots
determined by the motherboard manufacturer.
• Two terms frequently seen in motherboard memory
documentation are single-sided and double-sided.
▫ Single-sided memory refers to a memory module that the CPU
accesses at one time. In other words, the memory module has one
“bank” of memory and 64 bits are transferred out of the memory
module to the CPU.
▫ Double-sided memory means that a single memory module has
been developed in such a way that it actually contains two
memory modules in one container (two banks). If the
motherboard slot has been designed to accept this type of
memory module, data is still sent to the CPU 64 bits at a time.
• This is just a way for having more banks of memory on the
motherboard without requiring more memory slots.
• Another related topic is dual-channel memory.
Dual-channel means that the motherboard
memory controller chip handles processing of
memory requests more efficiently by handling
two memory paths simultaneously.
• Dual-channeling increases a system
performance. However, it only speeds things up
if the memory modules match exactly—same
memory type, same memory features, same
speed, and same capacity.
• Note that on some motherboards the memory
modules on Channel A or B do not have to be the
same capacities, but the total capacity of the
memory module in Channel A should match the
total capacity of the memory modules installed
in Channel B.
• Figure 6.6 illustrates this concept.
• To plan for the correct amount of memory, you
must refer to the motherboard documentation
and each motherboard is different.
• An example helps with this concept. Figure 6.7
shows a motherboard layout with four memory
slots.
▫ This motherboard allows 256MB, 512MB, 1GB,
and 2GB unbuffered non-ECC DDR2-533 240- pin
DIMMs for a maximum of 8GB. Pretend the
customer wants 1GB of RAM. What could we do?
• How many memory modules do we buy and
what capacities? Table 6.7 shows the possible
solutions.
• The best solution is the second one because it
has the largest capacity chips taking advantage
of dual-channeling.
Planning for Memory—Research and
Buy
• Notice in Table 6.8 (as in most memory advertisements)
that the memory capacity is shown first.
• Notice in Table 6.8 how the memory modules are DDR2
and show the PC2 rating. Later in the advertisement it
also shows the front side bus speed of 533 or 667 (MHz).
• Another listing in the memory advertisement shown in
Table 6.8 is the CL rating. CL (column address strobe
[CAS] latency), is the amount of time (clock cycles) that
passes before the processor moves on to the next
memory address.
• Also notice in Table 6.8 that the memory features are
listed—fully buffered, unbuffered, and registered.
• The voltage level for the memory module is shown (these
are standard values) as well as the capacity.
• With the capacity, if you see the number 64 at the end,
the module does not use parity. If you see 72, the
memory module uses either parity or ECC. The majority
of the time, it will be an ECC memory module.
Troubleshooting Memory Problems
The following tips and troubleshooting steps help with memory management:
• Add more RAM. To see the amount of physical memory (RAM) currently installed, rightclick the My
Computer or Computer Explorer option and click the Properties item.
• If you just installed new memory and an error appears, this is normal. Enter Setup because the BIOS
knows something has changed.
• If you just installed new memory and the computer will not boot, check your installation by pushing
harder on the memory module to ensure that it is fully seated into the slot. Check for loosened cables that
you might have caused. Ensure that you are installing the right memory type. You might need to upgrade
your BIOS so that your motherboard recognizes the increased amount of RAM.
• Delete files/applications that are no longer needed and close applications not being used. Empty the
Recycle Bin.
• Adjust virtual memory size.
• Change the virtual memory settings so that it uses more hard drive space.
• Do not put the swap file on multiple partitions that reside on the same hard drive. Use multiple hard
drives if necessary.
• Put the swap file on a hard disk partition that does not contain the operating system.
• Put the swap file on the fastest hard drive.
• Remove the desktop wallpaper scheme or use a plain one.
• Adjust your Temporary Internet Files setting. From Internet Explorer, click the Tools → Internet Options
→ Settings button. A slide bar allows you to adjust how much disk space is set aside for caching Web files.
To increase the amount of disk space (faster access), move the sliding bar to the right. For those who do
not have a lot of free hard disk space, move the sliding bar to the left.
• Defragment the hard drive. See Chapter 7 for steps.
• If you receive a message that the SPD device data missing or inconclusive, your motherboard is looking
for SPD data that it cannot receive from the memory module. If this is a new module, ensure it supports
SPD. If it is an older module, you need to replace one of your memory modules.
The end