The System Unit

The System Unit
Bays
A bay is an opening
inside the system unit in
which you can install
additional equipment
– A drive bay typically
holds disk drives
Buses
A bus allows the various
devices both inside and
attached to the system
unit to communicate with
each other
– Data bus
– Address bus
Word size is the number
of bits the processor can
interpret and execute at a
given time
Ports and Connectors
A port is the point at which a peripheral attaches to or
communicates with a system unit (sometimes referred
to as a jack)
A connector joins a cable to a port
Motherboard
A computer chip contains
integrated circuits
Expansion slot and Adapter
Cards
An expansion slot is a
socket on the motherboard
that can hold an adapter
card
An adapter card enhances
functions of a component of
the system unit and/or
provides connections to
peripherals
– Sound card and video card
Plug and Play, the computer automatically
can configure adapter cards and other peripherals
as you install them
Removable flash memory includes:
– Memory cards, USB flash drives, and PC
Cards/ExpressCard modules
Memory
Volatile memory
Loses its contents when power is
turned off
Example includes RAM
Dynamic RAM (DRAM)
Static RAM (SRAM)
Magnetoresistive RAM (MRAM)
Nonvolatile memory
Does not lose contents
when power is removed
Examples include ROM,
flash memory, and
CMOS
Read‐only memory (ROM) refers to memory chips
storing permanent data and instructions
A PROM (programmable read‐only memory) chip is a
blank ROM chip that can be written to permanently
CMOS technology provides high speeds and consumes
little power
Access time is the amount of time it takes the
processor to read from memory
Processor
Multi‐core processor
Dual‐core processor
Quad‐core processor
Power supply
The power supply converts the wall
outlet AC power into DC power
Some external peripherals have an AC
adapter, which is an external power
supply
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