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TECHNICAL COLLEGEDAYALBAGH EDUCATIONAL INSTITUTE

DAYALBAGH, AGRA

A course on

Maintenance of Computer Systems(Diploma in Electronics Engineering)

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What is Floppy?

A Floppy Disk is a data storage mediummade of thin magnetic coated flexible

("floppy") Teflon encased in a plastic shell.

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Invented by IBMInvented by IBM FDD in 8FDD in 8--inch (200inch (200 mm)mm)

55--inch (133inch (133 mm)mm)

33--inch (90inch (90 mm)mm)

FDD

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FDD

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FDD Rear View

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Floppy and its disk organization

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Floppy Disk Geometry & Density Chars.

Geometry

Specification

360 KB

5.251.2 MB

5.25720 KB

3.51.44 MB

3.52.88 MB

3.5

Tracks 40 80 80 80 80

Sectors/Track 9 15 9 18 36

Total

Sectors/Disk

720 2400 1440 2880 57600

Tracks Density

(TPI)

48 96 135 135 135

Bit Density (BPI) 5876 9869 8717 17434 34868

Density Name Double

Density

(DD)

High

density

(HD)

Double

Density

(DD)

High

density

(HD)

Extra High

density

(EHD)

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FDD Subassemblies

R / W Head Head Actuator

Spindle Motor Stepper Motor

Logic board Drive Select Sensor

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FDD Subassemblies..

Read/Write Heads

Converts binary data into electromagnetic

pulses and vice versa, when writing to /reading from the disk

Uses ferrite head, a iron core, wire wrappedaround it to form a controllable electromagnet

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FDD Subassemblies..

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FDD Subassemblies..

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FDD Subassemblies..

Works on contact recording technology i.e.,

the heads directly contact the disk media

Over a period of time, due to wear and

deposition of magnetic oxide and dirt demandperiodical cleaning

This makes the disk more sensitive to dirt

induces errors causing scratches and Pitts.

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FDD Subassemblies..

Head Actuator

A device that physically positions the read/writeheads over the correct track on the surface ofthe disk

A stepper motor

A motor that drives the Head Actuator

As time passes FDD can develop headalignment problemi.e., drifting of the positionof actuator

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FDD Subassemblies..

Head Alignment Problem leads to disk

failures when they are used in differentFDDs other than the FDD in which they are

formatted for..

Head actuators are slow in FDD that

makes theirseek timemuch higher

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FDD Subassemblies..

Spindle Motor

It is responsible to spin the diskThe speed of the spindle motor depends on

the type of FDD

360 KB 5.25 300 RPM

1.2 MB 5.25 360 RPM720 KB 3.5 300 RPM

1.4 MB 3.5 300 RPM

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FDD Subassemblies..

Logic Board

An integrated logic board that acts as the

drive controller

Controls all the other subassemblies and

circuits and components

Disk Change SensorA sensor that works in conjunction with FDC

to report, when a disk is ejected and a new

one is inserted

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Floppy Disk Controller (FDC)

FDC Functions

Translates the logical commands into

equivalent electrical pulses that control the disk

drive

Translates the stream of pulses generated byfloppy drive head into data in the form that can

be handled by PC

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FDC..

Major functional blocks of FDC

System interface logic

Floppy disk controller logic

Read / Write logic

Drive select logic

Control logic

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FDC Block Diagram

SYSTEMINETRFACELOGIC

FLOPPY DISK

CONTROLLERLOGIC

(FDC LOGIC)

R/WLOGIC

CONTROLLOGIC

DRIVESELECTLOGIC

FDD

R/W SIGNALS

DRIVE A

CONTROL B

SIGNALS

DRIVE B

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FDC.. The system interface logic communicates with

the system and the controller electronics through

I/O slots

Floppy disk controller logic (IC 8272)

coordinates all the functions of FDC

Although PC can support two FDDs the FDCcan be programmed to select only one of the twodrives at a time.

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FDC..

The drive select logic energizes the respective

drive for R / W operation after decoding the

commands received form CPU

R / W heads needs to be located over the

required track before actually honoring the R / W

request

The control logic issues commands to head

assembly to locate it over the desired address

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FDC..

The control logic also analyses the interface

signals such as write protect, index hole and

track 0 and informs CPU about the status

R / W logic decodes the commands from CPU,either to perform read / write operation

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Hard Disk Drive Subassemblies

Disk Platter

R / W Head

Head Arm / Head Slider

Head Actuator

Spindle Motor Logic Board

Air Filter

Bezel

Cables and connectors

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Disk Platter is fixed magnetic coatedaluminum / ceramic plate

General sizes :5.25, 3.5, 2.5

No. of platter vary from 1 10 in a HDD

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A Disk Platter

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Types of R / W HeadsFerrite

Metal in Gap

Thin film

Magneto Resistive

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R / W Heads

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Ferrite Head was originally used in HDDs

(Winchester drives) by developed IBM

It is made of iron oxide core wrapped with

electromagnetic coils

To write on to disk platter using this head the coilis energized which produces magnetic field on the

disk surface

To read from the disk head is passed over thedisk surface and the induced current generated in

the coil is used to read the data.

Obsolete

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A metal alloy is placed in the recording

gap on the trailing edge of the head in

Metal in gap type heads

Metal is placed using vacuum depositing

process called sputtering

Used in high density thin film media

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Thin file head are very small and light in

weight and are as close as 2 to the disksurface

These are produced by photolithographicprocess

Iron nickel alloy is used instead of iron oxide,

which is 2 4 time more powerful magnetically

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Magneto resistive head works on the principle

that when a magnetic field is present in near a

conductor, the resistance of the conductorchanges.

To read the data a small amount of current is

allowed to flow through the drive head and any

change in the current is measured.

A separate head is required to write data These are very delicate and susceptible to

electrostatic charges

H d Di k D i S b bli

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SPINDLE MOTOR


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It is the main motor which rotates the hard disk

drive platters.

It is called Spindle motor because it is directlyconnected to the Spindle on which the plattersare connected.

Spindle motor rotates at a speed of 3600 to7200 RPM or more.


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Logic Board is an intelligent circuit board in built

to the hard disk.

It contains the electronic components thatcontrols various sections of the HDD

It also acts as an interface between the hard

disk drive and the computer.

HDD S b bli

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HDD Subassemblies

HDD S b bli

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HDD Subassemblies

Air Filter

Most HDDs will have two air filters

Re-circulating air filter

Breather filter

HDD G t

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HDD Geometry

HDD O i ti

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HDD Organization

ArmAssembly Spindle Cylinder

HeadArm

PlatterTrack

HDD Geometry

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HDD Geometry

T k d S t

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Tracks and Sectors

Bits are grouped into sectors

Typical sector-size = 512 B of data

Sector also has overhead information

Error Correcting Codes (ECC)

Servo fields to properly position the head

Density

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Density

Density Metrics

Linear density

(Bits/inch or BPI) Track density

(Tracks/inch or TPI)

Arial Density = BPI xTPI

BPI

TPI

C it

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Capacity

Total no. of sides x no. of tracks/side xtotal sectors per track = Cylinders

Cylinders x Heads x Sectors x

bytes/sector = storage capacity

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Internal Data Rate (IDR)

Rate at which data can be read from or

written to the physical media

Expressed in MB/s

IDR is determined by

BPI

Platter-diameterRPM

Seeking

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Seeking

Seek time depends on: Inertial power of the arm actuator motor

Distance between outer-disk recording radius and inner-disk

recording radius (data-band) Depends on platter-size

Components of a seek: Speedup

Arm accelerates

Coast Arm moving at maximum velocity (long seeks)

Slowdown Arm brought to rest near desired track

Settle Head is adjusted to reach the access the desired location

Metrics for Drives

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Metrics for Drives

Traditional RPM

Seek time Capacity

New Metrics Acoustics (drives in living rooms)

Power (battery, cooling, )

Idle/Standby modes (Watts saved) Shock/Vibration (cabinets, other drives, jogging)

Reliability (end-to-end protection)

Interface technologies

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Interface technologies

ATA (Advanced Technology Attachment)

SATA (Serial ATA) PATA (Parallel ATA)

FATA ( a low cost ATA for Fiber opticchannel)

SCSI (Small Computer System Interface)

USB (Universal Serial Bus)

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Drive Electronics Common blocks found:

Host Interface

Buffer Controller

Disk Sequencer

ECC

Servo Control

CPU

Buffer Memory

CPU Memory

Data Channel

D i El i

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Drive Electronics

HDD Controller

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HDD Controller

B

U

S

B

U

S

DMA DISKCONTROLLER

SERVO

MOTORCONTROLLER

DATASEPARATOR

ROMSERVO P

SPINDLEDRIVER

PULSEDETECT.

DRIVEACTUAT.

HEADAND

DISK

ASSEMBLY

HDD Controller

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HDD Controller

System Interface Unit

Buffer RAM

BISO ROM

Timing control logic

HDC logic

Drive interface logic

HDD Controller

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HDD Controller

SYSTEMINTERFACELOGIC

RAM

___________

HDC LOGIC

___________

BIOS

R / W LOGIC

_______________

CONTROL LOGIC

HARD DISK

DRIVE

TIMER & CONTROL LOGIC

W

R

I/O

SLOTS

CONTROLSIGNALS

HDD Controller

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HDD Controller

SIL acts as a communication port between system andthe controller

HDC BIOS ROM determines what part of the disk is tobe read / write

This BIOS on HDC is also responsible to perform selftest of HDC whenever the system is started

HDC obtains address in terms of cylinder, head, sector,track from drive interface unit

HDD Controller

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HDD Controller

The control logic first verifies whether the requestedaddress is available in RAM and interprets the addressreceived and acts accordingly

The control logic also activates the spindle motor,instructs the head actuator to move read/write heads to

the appropriate track

The control logic also coordinates the flow of information

The timing and control logic controls the completesequence of operations

HDD Form Factors

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HDD Form Factors

Form factor Width Largest capacityPlatters

(Max)

5.25 146 mm 47 GB (1998) 14

5.25 146 mm 19.3 GB (1998) 4

1.3 43 mm 40 GB (2007) 1

1 (CFII/ZIF/IDE-

Flex)42 mm 20 GB (2006) 1

0.85

24 mm 8 GB (2004) 1

3.5 102 mm 3 TB (2010) 5

2.5 7 15 mm 15 TB (2010) 4

1.8 8 mm 320 GB (20090 3

Performance Characteristics

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Performance Characteristics

Data transfer rate

Power consumption

Audible noise

Shock resistance

Few important terms

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p

Head skew: The offset distance from the start of

the previous track, so that the head has time toswitch from top of platter to bottom of platter and

be at the start of the new track

Cylinder skew: The offset distance from thestart of the last track of the previous cylinder so

that the head has time to seek from cylinder to

cylinder and be at the start of the first track of

the new cylinder

Few Important Terms

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ZBR: Zone Bit Recording (ZBR) is usedby disk drives to store more sectors per

track on outer tracks than on inner tracks

LBA: In Logical Block Addressing, only

one number is used to address data, andeach linear base address describes a

single block.

Hard Disk Preparation !!!

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Choose a HDD

Look at the Jumper settings for suitable mode and set

them as requiredMaster

Slave

Cable Select etc.

Position the HDD in its bay and screw it properly

Connect the power cable (D type) running from SMPS

Connect data cable to suitable interface (IDE/SATA etc.)

Power on the system


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Invoke BIOS

Detect HDD through BIOS in suitable mode and reboot

the system with bootable disk

Initialize HDD (Optional) using FDISK program

Perform Logical division as required

Format all partitions

Set the active partition

Load OS on to a predetermined partition

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