EEL 4709c- Computer Design

Chapter 6External Memory

Team #6:Adriana Andino

Janos Magasrevy

1Chapter 6 :: External Memory

• Magnetic Disk– Magnetic Read and Write Mechanisms– Data Organization and Formatting

• Optical Memory– Compact Disk– Digital Versatile Disk

• USB Memory Stick

2Chapter 6 :: External Memory

Types of External Memory

• Disk substrate coated with magnetizable material (iron oxide…rust)

• Substrate used to be aluminium• Now glass

– Improved surface uniformity• Increases reliability

– Reduction in surface defects• Reduced read/write errors

– Lower flight heights (See later)– Better stiffness– Better shock/damage resistance

3Chapter 6 :: External Memory

Magnetic Disk

• Recording & retrieval via conductive coil called a head

• May be single read/write head or separate ones• During read/write, head is stationary, platter

rotates• Write

– Current through coil produces magnetic field– Pulses sent to head– Magnetic pattern recorded on surface below

• Read (traditional)– Magnetic field moving relative to coil produces

current– Coil is the same for read and write

• Read (contemporary)– Separate read head, close to write head– Partially shielded magneto resistive (MR) sensor– Electrical resistance depends on direction of magnetic

field– High frequency operation

• Higher storage density and speed

4Chapter 6 :: External Memory

Read and Write Mechanisms

• Concentric rings or tracks– Gaps between tracks– Reduce gap to increase capacity– Same number of bits per track (variable

packing density)– Constant angular velocity

• Tracks divided into sectors• Minimum block size is one sector• May have more than one sector per

block

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Data Organization and Formatting

• Messaging by audience• Target consumer demographics

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Disk Data Layout

• Bit near centre of rotating disk passes fixed point slower than bit on outside of disk

• Increase spacing between bits in different tracks

• Rotate disk at constant angular velocity (CAV)– Gives pie shaped sectors and concentric

tracks– Individual tracks and sectors addressable– Waste of space on outer tracks

• Lower data density• Can use zones to increase capacity

– Each zone has fixed bits per track– More complex circuitry 7Chapter 6 :: External Memory

Disk Velocity

8Chapter 6 :: External Memory

Disk Layout Methods Diagram

• Must be able to identify start of track and sector

• Format disk– Additional information not available to

user– Marks tracks and sectors

9Chapter 6 :: External Memory

Finding Sectors

10Chapter 6 :: External Memory

Winchester Disk Format Seagate ST506

• Originally for audio• 650MB giving over 70 minutes audio• Polycarbonate coated with highly

reflective coat, usually aluminium• Data stored as pits• Read by reflecting laser• Constant packing density• Constant linear velocity

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Optical Storage CD-ROM

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CD Operation: Material

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44,100 samples/channel/second x 2 bytes/sample x 2 channels x 74 minutes x 60 seconds/minute =

783,216,000 bytes

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CD Operation: The Spiral

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CD Operation: Bumps

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The incredibly small dimensions of the bumps make the spiral track on a CD extremely long. If you could lift the

data track off a CD and stretch it out into a straight line, it would be 0.5 microns wide and almost 3.5 miles (5 km)

long!

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CD Operation: Reading the disk

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• Audio is single speed– Constant linier velocity– 1.2 ms-1

– Track (spiral) is 5.27km long– Gives 4391 seconds = 73.2 minutes

• Other speeds are quoted as multiples (2X, 4X, 48X, etc.)

• Quoted figure is maximum drive can achieve

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CD-ROM Drive Speeds

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• Mode 0=blank data field• Mode 1=2048 byte data+error correction• Mode 2=2336 byte data

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CD-ROM Format

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• Difficult• Move head to rough position• Set correct speed• Read address• Adjust to required location

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Random Access on CD-ROM

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FOR:• Large capacity (debatable)• Easy to mass produce• Removable• RobustAGAINST:• Expensive for small runs• Slow• Read only

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CD-ROM for & against

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• CD-Recordable (CD-R)– Now affordable– Compatible with CD-ROM drives

• CD-RW– Erasable– Getting cheaper– Mostly CD-ROM drive compatible– Phase change

• Material has two different reflectivities in different phase states

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Other Optical Storage

Chapter 6 :: External Memory

• Digital Video Disk– Used to indicate a player for movies

• Only plays video disks• Digital Versatile Disk

– Used to indicate a computer drive• Will read computer disks and play video

disks• Dogs Veritable Dinner• Officially - nothing!!!

21Chapter 6 :: External Memory

DVD what’s in a name?

• DVD- Digital Versatile Disk. A technology for producing digitized, compressed representation of video information, as well as large volumes of other digital data

• DVD-R – DVD Recordable

• DVD-RW – DVD Rewritable

22Chapter 6 :: External Memory

DVD what’s in a name?

• Next Generation of Optical Disk - HD- DVD - 5 times storage capacity than traditional DVDs

• Blue-Violent Laser vs. Red Laser - Shorter wavelength (405nm) than red laser

(650nm)

23Chapter 6 :: External Memory

BD Blu-ray Disk

USB Memory Stick

24

1. Overview

2. Design and implementati

on

3. Uses 4. Advantages and

disadvantages

5. Comparison with other

portable storageChapter 6 :: External Memory

Design and Implementation

One end of the device is fitted with a single male type-A USB connector. Inside the plastic casing is a small printed circuit board. Mounted on this board is some simple power circuitry and a small number of surface-mounted integrated circuits (ICs). Typically, one of these ICs provides an interface to the USB port, another drives the onboard memory, and the other is the flash memory.Drives typically use the USB mass storage device class to communicate with the host.

:: Essential components• Male type-A USB connector. (1)• USB mass storage controller. (2) (OTi-2168)• NAND flash memory chip. (4)• Crystal oscillator. (5)

:: Additional components• Jumpers and test pins. (3)• LEDs. (6)• Write-protect switches. (7)• Unpopulated space. (8)• USB connector cover or cap.• Transport aid.• Expansion slot.

Chapter 6 :: External Memory 25

It can control up to 8 pieces of flash memory. The controller has write-protected ability to prevent writing data to flash. Has one LED control pin. Comprehensive application software for security function with Windows OS is also available.

This controller can operate in Win XP, Win2000, Windows Me, and Mac OS without any driver installation. :: Features

● Mass storage class controller with Universal Serial Bus interface● USB Specification Compliance   - Conforms to high-speed (480Mb/s) USB Specification, Version 2.0    - Meet bus power specification● Integrated USB transceiver    - Dynamic feedback control   - Stable slew rate, independent of external loading ● Integrated USB Serial Interface Engine (SIE)● Integrated RISC micro-controller   - High-performance RISC architecture    - Single cycle instruction execution● 12 MHz external clock ● 3.3 V power operation ● Integrated PLL (Phase Lock Loop)● Support up to 8 pieces of Flash memory with write-protected ability ● Support Infineon HYF33DS5128000ATC flash● Support wear-leveling algorithm ● Higher reliability: ECC on the fly● Automatic bad block management ● Supported OS:   Win XP, Win2K, Windows ME, Linux 2.4 above,   and MAC OS 9.0 & higher   Win 98/Win98SE driver available    Mac 8.6 mass storage driver available from Apple ● Support Auto-Run feature ● Configurable Vendor ID/Product ID (VID/PID) ● Small form factor - standard 48-pin TQFP and LQFP (7mmX7mm) package

Chapter 6 :: External Memory 26

OTi-2168 USB 2.0 Controller

Uses:: Personal data transport

:: Secure storage of data, application and software files

:: System administration

:: Computer repair

:: Application carriers

:: Computer forensics and law enforcement

:: Booting operating systems

:: Windows Vista ReadyBoost

:: Audio players

:: Music storage and marketing

:: Backup

Chapter 6 :: External Memory 27

Advantages:: Impervious to scratches and dust, and mechanically very robust.

:: Almost all personal computers support USB.

:: Store data relatively densely compared to many removable media.

:: Power efficient, have no fragile moving parts, small and light.

:: Work without installing device drivers on the computer.

:: The operating system can use any file system or block addressing scheme.

:: Extremely resistant to tough conditions.

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Advantages

YouTube video

:: They can sustain only a limited number of write and erase cycles before failure.

:: Most USB flash drives don’t include a write-protect mechanism. Write-protection is suitable for repairing virus-infected host computers without the risk of infecting the USB drive itself.

:: They are easily misplaced because of their small size. As a consequence of this, some manufacturers have added encryption hardware to their drives for data protection.

:: When they are compared to other portable storage device, for example external hard drives, USB drives have a high price per unit of storage and are only available in comparatively small capacities.

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Disadvantages

Comparison with other portable storage:: Obsolete devices

:: Tape

:: Floppy disk

:: Optical media

:: External hard disk

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1. What are the advantages of using glass substrate for a magnetic disk?

32Chapter 6 :: External Memory

Review QuestionsImprovement in the uniformity of the magnetic film surface to increase disk reliability. A significant reduction in overall surface defects to help reduce read/write errors. Ability to support lower fly heights (described subsequently). Better stiffness to reduce disk dynamics. Greater ability to withstand shock and damage.2. How are data written onto a magnetic disk?The write mechanism is based on the fact that electricity flowing through a coil produces a magnetic field. Pulses are sent to the write head, and magnetic patterns are recorded on the surface below, with different patterns for positive and negative currents.3. How are data read from a magnetic disk?In the traditional read mechanism, magnetic field moving relatively to the coil produces a current. When the surface of the disk passes under the head it generates current of the same polarity, as the one recorded on the disk..4. Explain the difference between a simple CAV system and a multiple

zoned recording system?For the constant angular velocity (CAV) system, the number of bits per track is constant. An increase in density is achieved with multiple zoned recording, in which the surface is divided into a number of zones, with zones farther from the center containing more bits than zones closer to the center..

5. What is the typical sector size?

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Review QuestionsA) 256 bytes. B) 1024 bytes. C) 512 bytes. D) 128 bytes.6. What’s the benefit of using Blue-Violet laser?The benefit of using a blue-violet laser (405nm) is that it has a shorter wavelength than a red laser (650nm), which makes it possible to focus the laser spot with even greater precision. This allows data to be packed more tightly and stored in less space, so it's possible to fit more data on the disc even though it's the same size as a CD/DVD. This together with the change of numerical aperture to 0.85 is what enables Blu-ray Discs to hold 25GB/50GB7. How long is the spiral track of a CD-ROM?A) 5 miles. B) 5.27 km. C) 4270 meters. D) There’s no spiral track on a CD-ROM.8. What are the essential components of a USB flash drive?Male type-A USB connector, USB mass storage controller, NAND flash memory chip, and crystal oscillator.9. What is the data transfer speed specification for USB V2.0?A) 600 Mb/s. B) 380 Mb/s. C) 480 Mb/s. D) 1 Gb/s.10. What’s the layer composition of a CD-ROM?Label, Acrylic, Aluminum, and Polycarbonate plastic.

References: Book and Related Websites

Book:

Computer Organization and Architecture By: William Stallings(Preferred)

Websites:

www.wikipedia.org http://www.blu-ray.com/info/ http://electronics.howstuffworks.com/cd.htm http://www.youtube.com/watch?v=NyOFIH-6WGs http://www.bress.net/blog/archives/114-How-Long-

Does-a-Flash-Drive-Last.html

34Chapter 6 :: External Memory