Lecture #6:
Expansion
Cards, Ports
and Buses
What we will learn about:
Expansion Slots
Expansion Cards
Ports
Buses
Bays
Power Supplies
1
Expansion cards
The circuit board used to add devices or
capabilities to the computer is called an
expansion card. Examples of expansion cards
are
z
z
z
video card
sound card
SCSI connections for external devices
Types of Expansion cards
- Video (or graphics) card – converts output to video signal
- Video Capture – used with a video camera (camcorder)
- Sound – speakers, microphone
- Modem – allows communications through phone lines
- Network Interface – allows communications to a network
- PC/TV – connect to a TV
- Game – connect a joystick
- Interface (port) – connect peripheral devices
2
PC cards and Flash Memory Cards
thin, credit card-sized device for adding memory, disk
drives, modem or other devices to a laptop or other
mobile device (like digital cameras).
z
z
z
Type I – memory
Type II – communications
Type III – hard drives
Unlike cards that plug into a motherboard, PC cards can
be changed while the device is running – called hot
swapping (plugging)
Ports
Ports, used to add keyboard, monitor, printer, etc.,
are places to attach external devices using
connectors.
A connector joins a cable to a device. Male
connectors have exposed pins, female connectors
have matching holes.
Different devices have different pin layouts.
3
Connectors (page 204)
Types of Ports
zSerial
Port – transmits only one bit of data at a time,
used to connect things that don’t require a fast
transmission time like a keyboard, mouse, or modem.
zParallel
port - transmits more than one bit of data at a
time, faster than serial ports.
zUSB
(universal serial bus) – can connect up to 127
different peripheral devices with a single connector
daisy chained together.
4
Special Purpose Ports
z
z
z
z
z
MIDI (musical instrument digital interface)
SCSI (small computer system interface) – high speed
parallel port for disk drives and printers
1394 or FireWire (like USB port) – connects multiple
devices
IrDA (InfraRed Data Association) – used for wireless
connections
Bluetooth – also used for wireless, uses radio waves
Buses
Buses are the electrical pathway (trace) along which bits
are transferred.
Used to transfer bits from:
z storage devices to memory
z input devices to memory
z memory to the CPU
z CPU to memory
z memory to output devices
z memory to storage devices
5
Bus Speed
z
A bus is measured by its size or bus width. The bus width
determines the number of bits that can be transferred at
one time. The larger the number of bits handled by the
bus, the faster the computer transfers data. (For example
a 64-bit number has to be transferred in two steps on a 32bit bus). The wider the bus, the fewer number of transfers
must be made.
z
Every bus has a clock speed (like the CPU). The faster the
clock, the faster the data can be transferred.
Two types of buses are:
z
System bus – part of the motherboard that
connects CPU to main memory (generally what
is meant by bus)
z
Expansion bus – allows CPU to communicate
with peripheral devices.
6
Expansion bus
fastest
next fastest
next fastest
slowest
memory
processor
PCI bus
expansion slots
ISA bus expansion slots
DVD-ROM
drive
Bays
CD-RW
drive
Zip drive
Open area inside the
system unit for
installing additional
equipment
empty drive
bay
floppy disk
drive
7
Be Sure you Know:
1.
The types of expansion slots and cards in the system unit
2.
The difference between a serial, a parallel,and a USB port
3.
How buses contribute to a computer’s processing speed
Reading Assignment
Read Chapter 5 in
Discovering
Computers 2005:
Input Devices
8