PRESENTATION ON

MEMORY UNITS

Presented by

Krishna

INTRODUCTION

In computing memory refers to the physical

devices used to store programs (sequences of

instructions) or data (e.g. program state

information) on a temporary or permanent

basis for use in a computer or other digital

electronic device.

TYPES OF MEMORY

There are two types of Memory.

They are :

Primary or main Memory &

Secondary Memory

PRIMARY OR MAIN MEMORY

Main memory is divided into two parts :

Random Access memory (RAM), should be

better known as Read Write Memory (RWM).

Read Only Memory (ROM) .

RANDOM ACCESS

MEMORY

(RAM)

A RAM memory chip is an integrated circuit

(IC) made of millions of transistors and

capacitors.

RAM is volatile memory, which means that it

requires

a steady flow of electricity to maintain its

contents.

As soon as the power is turned off, whatever

data was in

RAM is lost.

TYPES OF RAM

STATIC RAM

Semi conductor memory

Uses flip flop to store each bit of memory so does not need to be periodically refreshed

Fast and consumes low power

Expensive and has complex structure(6 transistors) so not used for high capacity applications

DYNAMIC RAM

Stores each bit of memory in capacitor in an

intrgrated circuit

Real capacitors leak charge so capacitors

need to be refreshed periodically

Simple structure (1 capacitor and 1 transistor

per bit) so it has very high density

READ ONLY MEMORY

(ROM)

New contents cannot be added

Used to store the instructions of routine type,

permanent in nature and used to control or

supervise the hardware

TYPES OF ROM

PROGRAMMABLE READ ONLY MEMORY

(PROM)

Programmed to record the information using a

facility PROM – programmer

Once the information is recorded it cannot be

changed

ERASABLE PROGRAMMABLE

READ ONLY MEMORY (EPROM)

Information can be erased and chip can be reprogrammed to record different information using PROM programmer

In formation is erased using UV radiations

It is of two types- Ultra Voilet Erasable Programmable Read Only Memory (UEPROM) and Electrically Alterable Programmable Read Only Memory (EAPROM

ELECTRICALLY ERASABLE

PROGRAMMABLE READ ONLY MEMORY

(EEPROM) Memory is erased by electrical signals

Provides easy means to store temporary or

permanent information in the form of ROM

memory

EEPROM is just like a flash memory.

Flash Memory is a special types of EEPROM

that can be erased and reprogrammed in

blocks instead of one byte at a time.

CACHE MEMORY

Faster and expensive than RAM

It improves the computer’s performance and is

less than 512 KB

Processor can use it to store frequently

accessed data and programs instructions

It is of two types – L1 / primary cache(inside

microprocessor) and L2/ secondary cache(in

the mother board or near the microprocessor)

Flash memory

Flash memory is an electronic non-volatile computer

storage medium that can be electrically erased and reprogrammed.

Introduced by Toshiba in 1984, flash memory was developed

from EEPROM (electrically erasable programmable read-only

memory). There are two main types of flash memory, which are

named after the NAND and NOR logic gates. The internal

characteristics of the individual flash memory cells exhibit

characteristics similar to those of the corresponding gates.

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SECONDARY MEMORY

By:ppkl

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History of secondary memory

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The Selectron tube

The Selectron tube had a capacity of 256 to

4096 bits (32 to 512 bytes). The 4096-bit

Selectron was 10 inches long and 3 inches

wide. Originally developed in 1946, the

memory storage device proved expensive and

suffered from production problems, so it never

became a success.

Punch cards18

Early computers often used punch cards for

input both of programs and data. Punch cards

were in common use until the mid-1970s. It

should be noted that the use of punch cards

predates computers. They were used as early

as 1725 in the textile industry (for controlling

mechanized textile looms).

Punched tapes19

Same as with punch cards, punched tape was

originally pioneered by the textile industry for

use with mechanized looms. For computers,

punch tape could be used for data input but

also as a medium to output data. Each row on

the tape represented one character.

Magnetic drum memory20

Invented all the way back in 1932 (in Austria), it was widely used in

the 1950s and 60s as the main working memory of computers. In

the mid-1950s, magnetic drum memory had a capacity of around 10

kB.

Above left: The magnetic Drum Memory of the UNIVAC

computer. Above right: A 16-inch-long drum from the IBM 650

computer. It had 40 tracks, 10 kB of storage space, and spun at

12,500 revolutions per minute.

Flash memory

Flash memory is an electronic non-volatile computer

storage medium that can be electrically erased and reprogrammed.

Introduced by Toshiba in 1984, flash memory was developed

from EEPROM (electrically erasable programmable read-only

memory). There are two main types of flash memory, which are

named after the NAND and NOR logic gates. The internal

characteristics of the individual flash memory cells exhibit

characteristics similar to those of the corresponding gates.

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Working of flash memory

Flash memory is a type of EEPROM chip, which stands

for Electronically Erasable Programmable Read Only

Memory. It has a grid of columns and rows with a cell

that has two transistors at each intersection (see image

below).

The two transistors are separated from each other by a

thin oxide layer. One of the transistors is known as

a floating gate, and the other one is the control gate.

The floating gate's only link to the row, or word line, is

through the control gate. As long as this link is in place,

the cell has a value of 1. To change the value to a 0

requires a curious process called Fowler-Nord heim

tunneling.

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Types of flash memory24

There are two main types of flash memory

NOR and NAND

Nor memory25

NOR flash is the faster memory, but

when having to erase and write data, it

takes longer.

Developed to replace read only memory

Full address and data buses allow

random access to any memory location

Can access any memory cell

Slow sequential access

Nand memory

The storage capacity of NAND is a lot more

than that of NOR, but the random access is

slow for it.

Developed to replace hard disks

Sequential-accessed command and data

registers replace the external bus of NOR

Decreases chip real estate

Can only access pages

Faster sequential access

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Types of flash memory27

SD Cards

Compact Flash

Cards

USB Drives

Memory Sticks

Smart Media Cards

Categories Of

Storage28

• Magnetic

– Floppy disks

– Zip disks

– Hard drives

• Optical

– CD-ROM

– DVD

• Solid state storage devices

– USB Key

Magnetic storage29

Magnetic storage (or magnetic recording) is

the storage of data on a magnetized medium.

Magnetic storage uses different patterns

of magnetization in a magnetizable material to

store data and is a form of non-volatile

memory. The information is accessed using

one or more read/write heads.

Magnetic drives30

Magnetic disc31

Flat, circular platter with metallic coating

that is rotated beneath read/write heads

Random access device; read/write head

can be moved to any location on the

platter

Hard disks and floppy disks

Cost performance leader for generalpurpose

on-line secondary storage

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Magnetic Drives: Storage Capacities

Floppy disks

~ 1 MB

Hard drives

~80 – 500 GB

Floppy discs33

A floppy disk, also called a diskette, is a disk storage medium

composed of a disk of thin and flexible magnetic storage medium,

sealed in a rectangular plastic carrier lined with fabric that removes

dust particles. Floppy disks are read and written by a floppy disk

drive(FDD).

Floppy disks, initially as 8-inch (200 mm) media and later in 5¼-inch

(133 mm) and 3½-inch (90 mm) sizes, were a ubiquitous form of

data storage and exchange from the mid-1970s well into the 2000s

Hard disks34

A hard disk drive (HDD)[b] is a data storage device used for storing

and retrieving digital information using rapidly rotating disks

(platters) coated with magnetic material.[2] An HDD retains its

data even when powered off. Data is read in a random-access

manner, meaning individual blocks of data can be stored or

retrieved in any order rather than sequentially. An HDD consists of

one or more rigid ("hard") rapidly rotating disks (platters)

with magnetic heads arranged on a moving actuator arm to read

and write data to the surfaces.

Optical Drives35

CD's (Compact Disk)

~ 700 MB storage

CD-ROM (read only)

CD-R: (record) to a CD

CD-RW: can write and erase CD to reuse it

(rewritable)

• DVD(Digital Video Disk)

Compact disc(cd)36

Compact disc (CD) is a digital optical disc data storage format. The

format was originally developed to store and play only sound

recordings but was later adapted for storage of data (CD-ROM).

Several other formats were further derived from these, including

write-once audio and data storage (CD-R), rewritable media (CD-

RW), Video Compact Disc (VCD), Super Video Compact Disc

(SVCD), Photo CD, Picture CD, CD-I , and Enhanced Music CD.

Audio CDs and audio CD players have been commercially available

since October 1982.

Standard CDs have a diameter of 120 millimetres (4.7 in) and can

hold up to about 80 minutes of uncompressed audio or about

700 MB of data. The Mini CD has various diameters ranging from

60 to 80 millimetres (2.4 to 3.1 in); they are sometimes used for CD

singles, storing up to 24 minutes of audio or delivering device

drivers.

DVD (Digital Video Disk)37

DVD (sometimes explained as "digital video disc" or "digital versatile disc"[4][5]) is a digital optical disc storage format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs can be played in multiple types of players, including DVD players. DVDs offer higher storage capacity than compact discs while having the same dimensions.

Pre-recorded DVDs are mass-produced using molding machines that physically stamp data onto the DVD. Such discs are known as DVD-ROM, because data can only be read and not written or erased. Blank recordable DVD discs (DVD-R and DVD+R) can be recorded once using a DVD recorder and then function as a DVD-ROM. Rewritable DVDs (DVD-RW, DVD+RW, and DVD-RAM) can be recorded and erased many times.

Blu-ray Technology38

Blu-ray Disc (BD) is a digital optical disc data storage format designed to supersede the DVD format, in that it is capable of storinghigh-definition video resolution (1080p). The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs andCDs.[4] Conventional (pre-BD-XL) Blu-ray Discs contain 25 GB per layer, with dual layer discs (50 GB) being the industry standard for feature-length video discs. Triple layer discs (100 GB) and quadruple layers (128 GB) are available for BD-XL re-writer drives.[5] The name Blu-ray Disc refers to the blue laser used to read the disc, which allows information to be stored at a greater density than is possible with the longer-wavelength red laser used for DVDs. The main application of Blu-ray Discs is as a medium for video material such as feature films and physical distribution of video games for the PlayStation 3, PlayStation 4 and Xbox One. Besides the hardware specifications, Blu-ray Disc is associated with a set of multimedia formats.

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