Higher Computing
Peripherals
What we need to know!
• Description of the use and advantages of buffers and spooling
• Description of a suitable selection of hardware, including peripherals,
to support typical tasks including production of a multimedia
catalogue, setting up a LAN in a school, development of a school
website
• Justification of the hardware selected in terms of appropriate
characteristics including resolution, capacity, speed, cost and
compatibility
• Description of the features, uses and advantages of solid state storage
devices including flash cards
• Description of the development trends in backing storage devices
• Description of the following functions of an interface: buffering, data
format conversion (serial to parallel and analogue to digital), voltage
conversion, protocol conversion, handling of status signals
• Distinction between parallel and serial interfaces
• Description and explanation of the current trends towards increasing
interface speeds and wireless communication between peripherals
and CPU
Interface
• An Interface is the hardware/software
needed to allow communication between
the CPU and its peripherals
• Functions include:
–
–
–
–
–
Buffering
Data format conversion
Voltage conversion
Protocol conversion
Handling status signals
Buffers
• What is a buffer used for?
• A buffer is an area of memory in a peripheral
device. For example, if you print a document the
document will be transferred at high speed into
the buffer in the printer. This frees the CPU to
work on other things. The data in the buffer can
then be printed at a speed with which the printer
can cope.
Buffers (Cont.)
• The use of buffers is a technique for improving
system performance.
– Peripherals operate at much slower speeds than the CPU.
Buffers help compensate for the difference.
– When transferring data out, the faster the transfer to a
peripheral the faster the CPU can return to other tasks.
– The use of buffers reduces the frequency which the CPU
gets interrupted.
Spooling
• SPOOLING (Simultaneous Peripheral
Operations On-Line) involves creating a
temporary file that is spooled (transferred) on to
hard disk. This file can then be printed from the
disk at a speed with which the printer can cope.
• The print-out is being printed in the
"background" whilst the processor is free to do
other things.
• SPOOLING tends to involve larger file sizes.
Data Format Conversion
• Data Format Conversion involves changing
the form of the data between the CPU and
peripheral.
• An example of this is serial to parallel
conversion and vice versa.
Serial Data Transmission
• Serial Data Transmission sends the bits for
each character along the same line.
• Serial data transmission is relatively slow
but is more effective over long distances,
e.g. a network.
Serial Data Transmission
AB= 65 =
A
0100 0001
B = 66 =
0100 0010
0
Clock = 017
8
7
6
5
4
3
90
11
13
15
12
14
16
1
2
1
0
0
0
00
10
01
Parallel Data Transmission
• Parallel Data Transmission send each bit of
data along separate lines.
• This means transmission of a byte requires
at least 8 lines.
• Parallel Data Transmission is fast but only
suitable for short distances.
Parallel Data Transmission
AB= 65 =
A
0100 0001
B = 66 =
0100 0010
Clock = 02
31
1
0
0
0
0
0
0
1
0
1
0
0
0
0
0
1
Serial to Parallel Conversion
Voltage Conversion
• Voltage conversion is required when the
peripheral operate using a different voltage
from that used by the processor.
• The CPU usually operates at 5 volts. Some
keyboards use a higher voltage.
• This voltage must be changed to 5 volts
from the keyboard interface.
Protocol Conversion
• A protocol is a standard set of rules that
enables the communication and data
transfer between computers or a computer
and its peripherals.
• Protocol Conversion is required to ensure
that the device can be understood.
Handling Status Signals
• Status signals are use to show if a
peripheral is ready to communicate.
• Signals for a printer may include:
–
–
–
–
Ready to receive data.
Busy.
Paper jam.
Out of ink.
Solid State Devices
• Solid State Devices have no mechanical or
moving parts.
• They use memory chips which can be
written and rewritten to.
• They are often packaged and sold as
‘flashcards’, removable chips that can be
stored in your pocket.
Solid State Devices (Cont.)
• There are 2 types:
– Flash ROM and Flash RAM (RAM need
power to keep the data).
• Flash ROM uses Electronically Erasable
Programmable Read Only Memory
Solid State Devices (Cont.)
• Advantages
– Faster access time than mechanical disks.
– Compact and lightweight.
– No moving parts so no sound is made.
Solid State Devices (Cont.)
• Disadvantages
– More expensive, per megabyte of storage, than
a hard disk.
– Have a limit to the number of times it can be
used. Between 100k and 300k write cycles.
Developing trends in backing
storage devices
• Increased Capacity
– DVD-Recordable capacity was increased to
8.4Gb with the introduction of the dual layer
drive.
– Blu-ray Disc (BD) the next generation of
optical discs can store up to 27 GB in a single
layer or 54 GB in a dual layer disc.
– Holographic Storage stores the data through
the full depth of the device rather than the
surface. This allows storage of up to
100Gb/in2.
Developing trends in backing
storage devices
• Faster interfaces are constantly being
developed allowing Reading and Writing
to/from peripherals far quicker.
• On the next slide are example of interface
technologies and their maximum transfer
rates.
Developing trends in backing
storage devices
Technology
Theoretical Maximum Transfer Rate
Apple Desktop Bus (ADB)
0.01 Mbps or 10 Kbps
Serial Port
0.23 Mbps or 230 Kbps
Geoport Port
2 Mbps
USB 1.1 at low data transfer rate
1.5 Mbps
USB 1.1 at high data transfer rate
12 Mbps
FireWire 400
400 Mbps
SCSI
1-40 MB/sec
Fast SCSI
8-80 MB/sec
Ultra SCSI-3
18-160 MB/sec
USB 2.0 at high data transfer rate
480 Mbps
FireWire 800 at 800 Mbps
800 Mbps
Developing trends in backing
storage devices
• Lower cost per unit of storage.
– In 1995 100Mb hard disk cost £ 300.
– In 2005 a 100 Mb ZIP disk cost £5 and a
512Mb USB flash memory cost £25.
– Now in 2008 a 16Gb USB flash memory cost
£40.
Wireless Connections
• Why use wireless
– You do not have wire trailing around the room.
– It gives you more portability.
– Peripherals can be placed around the room
without worrying about cable lengths.
Bluetooth
• This is a short range wireless transmission
systems that can be used with a Keyboard/
Mouse/ Printer and Modem.
• It can also be used on Mobile phones and PDA’s
• It has a range of 10 meters (or 100 meters with a
booster).
• Current maximum transfer rate of 3Mbps.
Wifi
• Wifi stands for Wireless Fidelity Alliance
and is used in wireless local area
networking.
• It has a range of up to 50 meters.
• Current maximum transfer rate of 54Mbps.
Selection of suitable Hardware
• You are required to select appropriate
hardware for the following tasks:
– Production of a multimedia catalogue.
– Setting up a Local Area Network in school.
– Development of a school website.
Production of a multimedia
catalogue
• A multimedia catalogue is a database of products
or items which contain a variety of media, such
as sound, graphics and video.
• The following hardware may be suitable:
– Digital video camera.
– Digital still camera.
– Graphics tablet
– Microphone (may be integrated)
– Sound card (may be integrated)
– Video capture card (may be integrated)
Justification of hardware
• When choosing the appropriate hardware
you must be able to justify it in terms of
–
–
–
–
–
Resolution
Capacity
Speed
Cost
Compatibility
Resolution
• An expensive professional standard of
video camera is not essential as
enlargements of images is not required.
• A still camera of 3 mega pixels resolution
would be appropriate.
Capacity
• A digital video camera with a minimum of
5 minutes recording time.
• A still camera a with 1 GB of flash
memory card would hold over 400 3
megapixel JPEGs.
• An additional Hard disk with around 80
Gigabytes may also be required.
Speed
• DVD-Recordable drive would not be
essential but desired.
• A drive with a fast write speed would also
be useful if many copies are required.
Cost
• Digital Still Camera (3 megapixels) less
than £100
• Digital Video Camera £300
• Hard Disk 80Gb £40
• Video capture card £60
• Sound card £30
• Graphics tablet £50
• CD-R £15 for 100
• DVD-R £15 for 25
Compatibility
• JPEG is a standard format for still images.
• Mini DV format is supported by a wide
rage of digital video cameras.
• Firewire is a standard interface for digital
video cameras.
• USB 2 is a standard interface for digital
still cameras.
Setting up a LAN in school.
• In order to connect to the network in
school, each computer system must have a
network interface card.
• Suitable cabling such as unshielded twisted
pair would be required.
• Depending on the topology chosen,
switches or hubs may be required.
Setting up a LAN in school.
• Justification
• Speed- A minimum of 100 Mbps including
hubs, switches and cabling.
• Cost- £50 per 200m, outlet boxes £5,
Server £2000, 40 port hub £100, 40 port
switch £1000.
• Compatibility- Ethernet is standard for
LAN. WiFi is standard for wireless
networking.
Development of a school website.
• Very little hardware is required other than
the basic computer system.
• A digital camera would be useful for
photographs although a video camera may
not be required as it is unlikely the web
pages would support embedded video.
Development of a school website.
• Justification
• Resolution- A digital camera of 2-3
megapixels
• Capacity- A still camera a with 1 GB of
flash memory card would hold over 400 3
megapixel JPEGs.
• Cost- around £100 for the camera.
• Compatibility- the developed website
should be tested on a range of browsers
using a variety of OS.
What we should now know!
• Description of the use and advantages of buffers and spooling
• Description of a suitable selection of hardware, including peripherals,
to support typical tasks including production of a multimedia
catalogue, setting up a LAN in a school, development of a school
website
• Justification of the hardware selected in terms of appropriate
characteristics including resolution, capacity, speed, cost and
compatibility
• Description of the features, uses and advantages of solid state storage
devices including flash cards
• Description of the development trends in backing storage devices
• Description of the following functions of an interface: buffering, data
format conversion (serial to parallel and analogue to digital), voltage
conversion, protocol conversion, handling of status signals
• Distinction between parallel and serial interfaces
• Description and explanation of the current trends towards increasing
interface speeds and wireless communication between peripherals
and CPU