1.0 Personal Computer Components
1.1 Identify the fundamental principles of using personal
A Floppy Disk Drive is a disk drive
that enables a user to save data to removable disk. Initially, FDDs used
the 5 1/4" floppy disks, and were later replaced with 3 1/2" disks.
However, with the advent of removable hard disks, and flash drives, many
computers no longer use floppy disk drives.
The Pentium motherboard provides a standard 34-pin connector for interfacing
with FDD. A 34-pin flat ribbon (see figure below) cable is used to connect the motherboard to
This cable connects the motherboard's FDD interface with one or two floppy disk
drives. Floppy Disk Controller (FDC) uses I/O address range 370 to 37Fh. FDD
divides the floppy disk into 80 tracks per side, with 9 or 18 512-byte sectors
per side. This provides the system with 720KB ( 737,280 bytes) or
1.44MB (1,474,560 bytes) of storage. For power supply, FDD uses a Berg connector
as shown in the figure (Title: Berg Connector) below.
The FDD controller is assigned the IRQ-6 in PC-compatible systems. The FDD
controller generates an interrupt signal each time it receives a Read, Write, or
Format command from the system.
|3.5" Floppy Disk Drive.
||Connector side of the FDD
Yellow wire: +12V
Red wire: +5V
Black wires: Ground.
Floppy Drive Interface Cable:
The FDD interface cable is used to connect the FDD to the motherboard.
Figure: A Five connector Floppy Interface Cable
The FDD cable in the figure shows traditional five connectors
configuration. It has connectors for 5.25" drives, as well as 3.5"
drives, and 34-pin wide. However, 5.25" drives are rarely used now-a-days.
"Cable Twist" in the floppy cable is located between the two pairs of
connectors intended "A" and "B" floppy drives. This twist
causes the drive at the end of the cable to appear as A: to the system and the
one in the middle to be as B:.
The hard disk drive (Abbreviated as HDD or HD) holds the main
storage media of a computer. A HDD consists of several platters (or hard disks)
along with head actuator, head arm secured in a chassis. A schematic diagram of
a HDD is shown in the figure below:
|Schematic of a Hard Disk Drive
||Photo of a HDD that has two concentric disks
The individual hard disks (platters) are used to store the information. The
storage is achieved by depositing a thin magnetic film on either side of each
disk. The disks are mounted on a rotary drive.
Basically, the surface of each disk is divided into concentric Tracks. Then
each track is divided into Sectors. The data is accessed by specifying the disk
number, track number, and the sector number. The disks rotate at a very high
speed ( several thousands of revolutions per minute), enabling very fast read
and write operations. The magnetically sensitive head reads/writes information
when the disks rotate. The disks are sealed to prevent any dust or moisture
entering the drive.
|A typical hard disk drive is shown in the figure.
Hard Disk Drive Interfaces:
There are several standards connected with the Hard Disk Drives.
These include the following:
IDE/EIDE Hard Disk Drives:
IDE (Integrated Drive Electronics), also known as ATA, is used
with IBM compatible hard drives. IDE and its successor, Enhanced IDE (EIDE), are
the commonly used with most Pentium computers..
Figure: A 40-pin IDE cable connector
Enhanced IDE (EIDE) is the enhanced version of IDE technology,
and supports faster access to the hard disks.
Small Computer Systems Interface (SCSI):
SCSI (Pronounced as Skuzzi) is commonly used with server grade machines. IDE supports only two
drives (one master drive and one slave drive) per channel, whereas SCSI can
support 8 or more hard drives. There are different versions of SCSI available
today. Different versions of SCSI include the following:
The various SCSI bus standards primarily differ in the
Maximum throughput (MB/sec)
Maximum cable length, and
Maximum number of devices that could be connected.
For example, SCSI-I has a throughput of 5MB/sec, where as SCSI-3
can go up to 40MB/sec.
Serial ATA (SATA):
Serial ATA (SATA) is a next generation technology based on ATA,
and for transfer of data to and from a hard disk. Earlier, ATA was used to mean
parallel transfer of bits between the motherboard and the hard drive. However,
with the advent of SATA, traditional ATA was named as PATA (Parallel ATA).
IDE/EIDE is usually associated with PATA.
CD / DVD / RW (e.g. drive speeds, media types)
A CD-R stands for Compact Disc-Recordable. CD-R holds large
volumes of data, in the range of 100s of MB, and replaced Floppy Disk Drives
gradually. CD-R allows only one "Write" operation, and any number of
"Read" operations. CD-RW stands for Compact Disc -ReWritable.
CD-Rs resemble DVDs as their physical dimensions are the same.
The disks come in the dimensions of 120 mm (4.72 inches) or sometimes 80 mm
(3.15 inches) in diameter. The technology used in CD-R, and DVD manufacture and
information storage is completely different. DVDs have much higher storage
density compared to CD-R or CD-RW.
CD-R or CD-RW comes in different speeds. At 1x a recorder writes
150 KB (153,600 bytes) of data per second and at a multiple of that figure at
each speed increment above 1x.
||1x - 4x
||4x - 12x
||16x - 24x
. An IDE CDROM drive is shown in the figure below:
|Front side of an IDE CDROM Drive
||Back side of an IDE CDROM drive
Majority of IBM compatible PCs use IDE connector (or
CDROM drives. Most of the HDDs use IDE/EIDE connectors. To avoid conflict
between the two, CDROM drive is designated as "Slave", and the HDD is
designated as "Master". The "Master", and "Slave"
setting is typically done by configuring jumpers at the back of the CDR or HDD.
The IDE controller recognizes the "Master" and "Slave"
settings and chooses the correct device.
DVD stands for Digital Video Disk (Also known as Digital Versatile Disk).
Essentially, DVD looks very similar to CD-R, but contains larger storage space
and can hold video, audio, and/or computer data. A single-layer, single-sided
DVD has a capacity of 4.7GB where as a CD-ROM has a capacity of around 650MB. A
double-layer, double-sided DVD-ROM disk can have capacity over 17GB. The DVD
specification supports access rates of 600KBps to 1.3MBps.
DVD-R is a once-recordable form of DVD. DVD-RW or
DVD-R/RW can be written
multiple times. Many DVD drives can read data from a CD-R. But, some DVD drives
may not be able to read CD-Rs. You need to ensure compatibility with CD-R when
procuring a DVD drive. Normally, CD-R drives are not compatible with DVD, and
you will not be able to read a DVD using a CDR.
The original speed rating for DVDs is different from that of a CD-R. For a
DVD, 1x is 1352.54KB/sec. Following the convention, 2x for a DVD drive is
2,705KB/sec, 4x is 5,410KB/sec, 8x is 10,820KB/sec, and 16x would be
A DVD drive is shown in the figure above. It looks very similar to that of a
Removable storage (e.g. tape drive, solid state such as
thumb drive, flash and SD cards, USB, external CD-RW and hard drive)
Thumb drive or Flash drive is a portable memory storage. It is
and holds its data without a power supply, unlike RAM. Thumb drives will fit
into USB port on a computer and hot-swappable, which means a user can plug the
drive into a computer and will not have to restart it to access the drive. The
name thumb drive is derived from the characteristic of the drive, which is
about the size of a human thumb. Thumb drives, unlike Floppy disks, are very
stable and reliable. Unlike FDD or HDD, Flash drives have no moving parts, and
therefore more robust.
||Floppy disk Vs. Thumb drive (see relative sizes)
External hard drives:
These are best suited for back-up and storage of large amounts
(several hundreds of GBs) of data. As of now, technology doesn't allow several
hundreds of GBs to be stored in Flash drives, whereas Hard disks can store such
Tape drives: Tape drives are one of the oldest forms of
backup media. Tape drives are particularly useful if you have to take 100's of
GBs of backup.
External CD RW: These drives are also used for taking
backup. CD R or CD RW drives are useful for taking backup up to a few GB.
However, if you need to take huge amounts of backup, a tape backup is normally
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