Chp08_Storage Devices [Compatibility Mode]

7/23/2019 Chp08_Storage Devices [Compatibility Mode]

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Storage Devices

Types:1. Temporary storage

- stores data temporarily while its in use

Ex. RAM, ROM

Read-Only Memory(ROM)

- data cannot be changed, as its name implies

- it is non-volatile( which means that it can keepits contents even without power source)

- ideal for storing the PCs startup instructions andsystem BIOS


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Types of ROM:

1. PROM (programmable read-onlymemory)

- this type of ROM chip is programmedusing a special type of programmingdevice called a PROM burner which

permanently stores machinelanguage code on the PROM chip.


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2. EPROM(Erasable Programmableread-only memory)

- type of ROM that can beprogrammed and reused

- has a quartz window on the face ofthe chip that exposes the chipsinterior circuit. When ultraviolet(UV)light is shined through this window,it causes a chemical reaction thaterases the EPROM


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ROM with BIOS

BIOS: Basic Input/Output System


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3. EEPROM(Electronically erasable

programmable read-only memory)

- can be programmed like the EPROMbut it doesnt need to be removed

from the PC, can be reprogrammed,a process called flashing, using aspecialized software that runs onyour PC.

- also referred to as flash ROM


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b. RAM(Random Access Memory)

- is used in the PC for its primary memory

- where all active programs and data are storedso that they are readily available and easilyaccessed by the CPU and other components ofthe PC.

- a volatile form, when it loses its power, it losesits contents.

- much faster than a hard disk(8 to 16milliseconds to access data)

- RAM(50 to 80 nanoseconds)

Random Access refers to the ability to access asingle storage location in RAM without touchingthe locations that neighbor it.


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Random Access Memory


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UNIT of MeasureUnit Size Description

Bit One binary digit stores either binary 0 or 1

Byte Eight bits one character

Word 16 to 64 bits numeric values and addresses

Kilobyte(KB) 1 thousand bytes about one page ofdouble-spaced text

Megabytes(MB) 1 million bytes about the size of a shortbook

Gigabyte(GB) 1 billion bytes 1,000 short books

Terabyte(TB) 1 trillion bytes an entire library

Petabyte(PB) 1 quadrillion bytes just about all librariesin the US


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CPU

RAM

CPUREGISTERS

1. CPU requests data from RAM

2. RAM locates data and is ready to transfer

3. Data moves to CPU registers

RAM Operations :


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RAM Types :

1. Static RAM

- faster than DRAM, but is much moreexpensive and requires a much larger

physical space to store the same amount ofdata as DRAM.

- most commonly used for cache memory(located between the processor and RAM,

holds data and instructions that it getsfrom RAM to provide high-speed access bythe processor)


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2. DRAM (Dynamic RAM)

- is inexpensive and stores the largestnumber of bits in the smallestamount of physical space.

- has a cell, which stores one bit andmade up of capacitor(stores eitherpositive or negative voltage valuethat is used to represent 1 or 0

values)


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Types of DRAM :

DIP Packaging

- mounted into

individual sockets

directly on the

motherboard in banks

of four or more chips.

- found in oldersystems(386DX)


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SIMM(Single InlineMemory Module)

- earliest type ofmemory module

- consists of DRAMchips soldered to asmall circuit boardwith either a 30 or 72pin connector

- storage capacity thatranges from 1 MB to128MB


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DIMM(Dual InlineMemory Modules)

- 168-pin module

includes DRAM

memory on both sidesof the module and

supports larger

amounts of memory

capacity.


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2. Secondary storage

- stores data permanentlyEx. Hard disk, floppy disk

Hard disk

Major Components

1. Disk platters- primary unit of a harddisk

- its disks are the storage media for the disk

drive and it is on them that the data isactually recorded

- materials used are aluminum and alloysand glass


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Hard Disk Drive (HDD)


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2. Spindle Motor

- is a brushless and sensorless DC motor that isattached directly to the disk spindle

- motor that rotates the spindle and the disks

mounted to it.

Two types of spindle motor :

1. in-hub motors

- placed inside the HAD

2. bottom-mount motors- attached to the spindle outside the HAD


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3. Storage media

- the magnetic material that holds onthe platters

- thin layer of magnetic substance in

which electromagnetic data is stored.4. Read/Write Heads

- are connected to the same actuator

mechanism, which moves the headsin unison in and out, from the spindleto the edge of the platter.


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5. Head Actuators

- used to move3 the read/write headsof the hard disk

- used to extend and retract the heads

so that data can be read from orwritten to the disk platters.

Example : stepper motor actuator

voice coil actuators


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7. Air filters

- sealed permanently inside the HAD and never tobe changed

- designed to last the life of the drive

Two filters :

Recirculating filter- is to trap any particles of media that mayscraped off the disks by the read/write heads orany small particles that may have been trappedin the HDA during manufacturing.

Barometric or breather filter

- a vent that allows to equalize the air pressure.


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8. Connectors and jumpersThree types :1. data connector or interface connector- carries both the data and command

signals from the controller and CPU to andfrom the disk drive.

2. power connector- is the standard power connector available

from the PCs power supply that suppliesthe disk

3. jumpers- are used to configure the drive as a

master or slave on a shared interface, aswell as other configuration settings.


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COMPACT DISC-READ-ONLY-MEMORY (CD-

ROM)

Holds 640 million bytes of data

The most common method of softwaredistribution and data storage


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DIGITAL VERSATILE/VIDEO DISC

(DVD) Can store the equivalent of 17

gigabytes (GB) or about 25 timesmore than the CD-ROM

Can store hours of high quality audiovisual content such as the full-lengthmovie

Drives are able to read CD formatting Uses a read mechanism that includes

dual focus pick-up to read the disc


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EXPANSION CARDS Used to improve video performance,

add or improve the sound system,additional or new ports orconnectors, provide a networkconnection.

Improve or add capabilities of a PC


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Expansion Buses

ISA (Industry Standard Architecture)- 16 bit card

EISA(Extended ISA) - 32 bits card

VESA local bus (Video Electronics Standards

Association) - for 486 processors

PCI (Peripheral Component Interconnect)

- common on PCs today

AGP (Accelerated Graphics Port)- developed to improve 3D graphics


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COMPUTER HARDWARE

DIAGRAM


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Chp08_Storage Devices [Compatibility Mode]

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