Memory

Random Access Memory Defined

What is memory?

operating system and other system software that control the usage of the computer

equipment

application programs that carry out a specific task

data being processed by application programs

Three basic items stored in memory

Temporary storage place for data, instructions, and information

Consists of one or more chips on the motherboard or some other circuit board

MemoryMemory

How is memory measured? Size of memory is measured by the number of

bytes available

• Kilobyte - 1,024 bytes

• Megabyte - one million bytes

Volatile MemoryVolatile MemoryLoses its contents when Loses its contents when the computer's power is the computer's power is

turned offturned off

volatile memoryLoses its contents when the computer's power is

turned off

MemoryMemory

What are the two types of memory in the system unit?

nonvolatile memory

Does not lose its contents when the

computer’s power is turned off

MemoryMemory

Memory chips that can be read from and written to by the processor and other devices

When the computer starts, operating system files are loaded from a hard disk into RAM

What is random access memory (RAM)?

As additional programs and data are requested, they also load from storage into RAM

Most RAM is volatile

Storage (hard disk)

RAM

Step 3: When you quit Word, RAM may be used to store another program or data. The program is removed from the screen and the operating system’s user interface redisplays.

Step 1: When your computer is running, certain operating system files are in RAM. Shown here is the operating system’s user interface.

Step 2: When you start a word processing program such as Word, the program loads into RAM from a hard disk. As you create a document, it is in RAM and displays on your screen.

Step 4: When you start a spreadsheet program such as Excel, the program loads into RAM from a hard disk. As you create a spreadsheet, it is in RAM and displays on your screen.

MemoryMemory

How are applications transferred in and out of RAM?

Step 5: When you quit Excel, RAM may be used to store another program or data. Excel is removed from your screen and the operating system’s user interface redisplays.

MemoryMemory

What is a memory module?

single inline memory modules (SIMMs)

Rambus® inline memory module (RIMM)

Small circuit board with RAM chips, which are smaller in size than processor chips

Inserts into the motherboard Three types: SIMMS, DIMMS, and RIMMS

dual inline memory modules (DIMMs)

• FPM-Fast Page Mode DRAM -traditional DRAM

•EDO-Extended Data Output -increases the Read cycle between Memory and the CPU

•SDRAM-Synchronous DRAM -synchronizes itself with the CPU bus and runs at higher clock speeds

•RDRAM-Rambus DRAM -DRAM with a very high bandwidth (1.6 GBps)

•EDRAM-Enhanced DRAM -(dynamic or power-refreshed RAM) that includes a small amount of static RAM (SRAM) inside a larger amount of DRAM so that many memory accesses will be to the faster SRAM. EDRAM is sometimes used as L1 and L2 memory and, together with Enhanced Synchronous Dynamic DRAM, is known as cached DRAM.

SIMM vs. DIMM vs. RIMM? SIMM-Single In-line Memory Module DIMM-Dual In-line Memory Modules RIMM-Rambus In-line Memory Modules

SIMMs offer a 32-bit data path while DIMMs offer a 64-bit data path. SIMMs have to be used in pairs on Pentiums and more recent processors

RIMM is the one of the latest designs. Because of the fast data transfer rate of these modules, a heat spreader (aluminum plate covering) is used for each module

MemoryMemory

What is a memory module?

dual inline memory module (DIMM)

memory chip

RAM chips usually reside on a small circuit board which inserts into motherboard

MemoryMemory

What is read-only memory (ROM)?

BIOS

(basic input/output system)

Stored on ROM

Sequence of instructions the computer follows to

load the operating system and other files when you first turn on the computer

Nonvolatile — Contents not lost

when the computer is turned off

Memory chips that contain data, instructions, or information that is recorded permanently

Data can only be read,

cannot be modified

Read Operation•On a read the CPU will first try to find the data in the cache, if it is not there the cache will get updated from the main memory and then return the data to the CPU.

Write Operation • On a write the CPU will write the information into the

cache and the main memory.

Managing memory

Use of memory software accelerator Assigning the memory page file Dumping memory Memory planning based on the possible

program required loads

Common Memory Problems Terminal corrosion

PCB Socket

Broken PCB lines Defective memory chips Cold solder Burn component

Breaking Down the Memory Over heat Over voltage Overloading Incompatibility issue Wrong type of memory Defective motherboard Defective socket

Evolution of Memory 1970 RAM / DRAM 4.77 MHz 1987 FPM 20 MHz 1995 EDO 20 MHz 1997 PC66 SDRAM 66 MHz 1998 PC100 SDRAM 100 MHz 1999 RDRAM 800 MHz 1999/2000 PC133 SDRAM 133 MHz 2000 DDR SDRAM 266 MHz 2001 EDRAM 450MHz

Memory Versus Storage

What is storage?

The media on which data, instructions, and information are kept, as well as the devices that record and retrieve these items

Memory Versus Storage

How does storage differ from memory?

When you want to work

with a file, you remove it from storage

and place it in memory

When you are finished with the file, you

remove it from memory and return it to

storage

Storage also called secondary storage, auxiliary storage, permanent storage, or mass storage

Storage holds items such as data, instructions, and information for future use

Storage is nonvolatile

Memory Versus Storage

What is a storage medium and a storage device?

storage medium

The physical material on which a computer

keeps data, instructions, and

information

storage device

The computer hardware that records and retrieves items to

and from a storage medium

Writing

Process of transferring items from memory to a storage medium

Serves as a source of output

Memory Versus Storage

What is reading and writing?

Reading

Process of transferring data, instructions, and

information from a storage medium into

memory

Serves as a source of input

Memory Versus Storage

What is access time? The amount of time

it takes the device to locate an item on a disk

Defines the speed of a disk storage device

Memory (RAM)

Compact Disc

Floppy Disk

Tape

Hard Disk

cost

less

exp

ensi

ve

mor

e ex

pens

ive

speed

faster

slower

Memory Versus Storage

What is capacity? The number of

bytes (characters) a storage medium can hold

Manufacturers use many terms to define the capacity of storage media

Storage Term Abbreviation Number

of bytes

Kilobyte

Megabyte

Gigabyte

Terabyte

Petabyte

KB

MB

TB

GB

PB

1 thousand

1 million

1 billion

1 trillion

1 quadrillion

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