James A. Senn’s
Information Technology, 3rd Edition
Chapter 4
The Central Processor
and Memory
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© 2004 Pearson Prentice Hall
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Objectives
• Describe the components and purpose of the
central processing unit (CPU).
• Distinguish between primary storage (also
called memory) and secondary storage (also
called storage), and between RAM and ROM.
• Describe the chips and boards that can be
used to augment the CPU and main memory.
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Objectives (Continued)
• Explain the process by which computers use
registers to process data.
• List and explain the four determinants of
processor speed.
• Describe eight ways of increasing processing
and computer speed.
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The Central Processing Unit (CPU)
Definition
• Central Processing Unit (CPU) or Processor:
The computer hardware that executes program
instructions and performs the computer’s
processing actions.
• Integrated Circuits/Chip/Microchip: A collection
of thousands or millions of transistors placed
on a small silicon chip.
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The Central Processing Unit (CPU)
Definition (Continued)
• Transistor: An electrical switch that can be in
one of two states: open or closed.
• Integrating: The process of packing more
transistors onto a single chip.
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The Central Processing Unit (CPU)
Definition (Continued)
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The Central Processing Unit (CPU)
Control Unit
• Control Unit: The part of the CPU that oversees
and controls all computer activities according
to the instructions it receives.
• Instructions: Detailed descriptions of the
actions to be carried out during input,
processing, output, storage, and transmission.
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The Central Processing Unit (CPU)
Arithmetic/Logic Unit (ALU)
• Arithmetic/Logic Unit (ALU): The part of the
CPU that performs arithmetic and logical
operations.
– Arithmetic Operations: Addition,
Subtraction, Multiplication, and Division.
– Logical Operations: Greater Than (>), Less
Than (<), Equal To (=)
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Memory
Definition
• Primary Storage/Primary Memory/Main
Memory/Internal Memory: Storage within the
computer itself. Primary memory holds data
only temporarily, as the computer executes
instructions.
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Memory
Definition (Continued)
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Memory
Memory Size
• Byte: A storage location in memory; the
amount of memory required to store one digit,
letter, or character.
• Kilobyte/K-byte/KB/K: One thousand bytes.
• Megabyte/M-byte/MB/Meg: One million bytes.
• Gigabyte/G-byte/GB/Gig: One billion bytes.
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Memory
Memory Size (Continued)
• Terabyte/T-byte/TB: One trillion bytes.
• Address: An identifiable location in memory
where data are kept.
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Memory
RAM and ROM
• Random-access Memory (RAM): Memory that
permits data or information to be written into
or read from memory only as long as the
computer is turned on.
• Read-only Memory (ROM): A type of storage
that offers random access to memory and can
hold data and information after the electric
current to the computer has been turned off.
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Memory
Flash Memory
• Flash Memory: Memory that retains it contents
even when electricity is turned off.
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Memory
RAM, ROM and Flash Memory
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Memory
PCMCIA Card Memory
• PCMCIA Card/PC card: A card designed to
expand a computer’s memory.
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Memory
Definition
• Boot: To turn on the computer system and let the built-in
self-test run.
• Cold Boot: The system is turned on and started from an off
state. The CPU invokes the ROM BIOS boot program, which
in turn, runs the power-up self-tests and loads the
operating system from disk storage.
• Warm Boot: In a restart, the BIOS knows the system is
already running (data is written in a specific memory
location checked by the BIOS) and skips the power-on test.
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Inside the System Unit
Definition
• Board: A hardware device onto which chips
and their related circuitry are placed.
• System Unit: The hardware unit that houses a
computer’s processor, memory chips, ports,
and add-in boards.
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Inside the System Unit
Processor Chips
• Microprocessor: The smallest type of
processor, with all of the processing
capabilities of the control unit and ALU located
on a single chip.
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Inside the System Unit
Evolution of Intel Pentium Family of
Microprocessors
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Inside the System Unit
Intel Microprocessors
• Intel Celeron Processors
• Intel Pentium-M Processors
• Intel Celeron-M Processors
• Intel Xeon Processors
• Intel Itanium Processors
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Inside the System Unit
Evolution of Microprocessors for
Macintosh Computers
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Inside the System Unit
Other Microprocessor Chips
• AMD
• Digital Equipment Corp.
• Hewlett-Packard
• MIPS Technologies
• Sun Microcomputers
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Inside the System Unit
Memory Chips
• Single In-line Memory Module (SIMM): A
multiple-chip memory card inserted as a unit
into a predesignated slot on a computer’s
system board.
• Installed Memory: The amount of memory
included by a computer’s manufacturer on its
memory board.
• Maximum Memory: The most memory that a
processor can hold.
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Inside the System Unit
Ports
• Port: A connector through which input/output
devices can be plugged into the computer.
• Expansion Slot: A slot inside a computer that
allows a user to add an additional circuit
board.
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Inside the System Unit
Universal Serial Bus
• Universal Serial Bus (USB): A general purpose
port that can connect up to 128 devices, and
also hot swappable, meaning that devices can
be plugged in or unplugged without having to
shut down or reboot the system.
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Inside the System Unit
Add-In Boards
• Add-in Boards: A board that can be added to a
computer to customize its features and
capabilities.
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Inside the System Unit
Add-In Boards (Continued)
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Inside the System Unit
Plug and Play
• Plug and Play: The ability to install devices
into a computer when the computer itself
makes any necessary internal adjustments.
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The Processing Sequence
The Machine Cycle
• Machine Cycle: The four processing steps
performed by the control unit: fetch, decode,
execute, and store.
• Instruction Cycle (I-cycle): The first two steps
of the machine cycle (fetch and decode), in
which instructions are obtained and translated.
• Execution Cycle (E-cycle): The last two steps
of the machine cycle (execute and store),
which produce processing results.
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The Processing Sequence
The Machine Cycle
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The Processing Sequence
Registers
• Register: A temporary storage area in the processor that
can move data and instructions more quickly than main
memory can, and momentarily hold the data or
instructions used in processing as well as the results
that are generated.
• Four types:
– Storage Registers
– Address Registers
– Accumulators
– General-Purpose Registers
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Processor Speed
Definition
• Millisecond: One thousandth of a second
• Microsecond: One millionth of a second.
• Nanosecond: One billionth of a second.
• Picosecond: One trillionth of a second.
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Processor Speed
Definition (Continued)
• Millions of Instructions per Second (MIPS): The
number of instructions the processor can
execute per second – a measure of processor
speed.
• Megaflops: Millions of floating point operations
per second – a measure of how many detailed
arithmetic calculations the computer can
perform per second.
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Processor Speed
Determining Processor Speed
• Four elements:
– System Clock
– Bus Width
– Word Size
– Available Memory
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Processor Speed
Determining Processor Speed
(Continued)
• System Clock: A circuit that generates
electronic impulses at a fixed rate to
synchronize processing activities.
– Megahertz (MHz): Millions of electric pulses
per second – a measure of a computer’s
speed.
– Gigahertz (GHz): Billions of pulses per
second.
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Processor Speed
Determining Processor Speed
(Continued)
• Bus Width
– Input/Output (I/O) bus: A bus (electronic
circuit) that moves data into and out of the
processor.
– Data Bus: A bus that moves data between
the central processor and memory.
• Word Size
– Word: The number of bits a computer can
process at one time.
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Processor Speed
Determining Processor Speed
(Continued)
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Processor Speed
Determining Processor Speed
(Continued)
• Cache Memory: A form of high-speed memory
that acts as a temporary holding/processing
cell.
• Coprocessors: A special-purpose chip
mounted on a processor board; it is designed
to handle common functions quickly and
efficiently.
• Accelerator Boards: An add-in circuit board
that increases a computer’s processing speed.
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Processor Speed
Determining Processor Speed
(Continued)
• Reduced Instruction Set Computer (RISC)
– Complex Instruction Set Computing (CISC): A
computing instruction set that moves data to and
from main memory so often that it limits the use of
registers.
– Microcode: The instructions that coordinate the
execution of the instructions to move data and from
memory.
– Reduced Instruction Set Computing (RISC): A
computing instruction set that takes data for the
execution of an instruction only from registers.
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Processor Speed
Determining Processor Speed
(Continued)
• Pipelining: A computer starts processing a
new instruction as soon as the previous
instruction reaches its next step in the
processing cycle.
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Processor Speed
Determining Processor Speed
(Continued)
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Processor Speed
Determining Processor Speed
(Continued)
• Parallel Processing: Processing in which a computer
handles different parts of a problem by executing
instructions simultaneously.
– Sequential Processing: Processing in which the
execution of one instruction is followed by the
execution of another.
– Single Instruction/Multiple Data (SIMD) method: A
parallel-processing method that executes the same
instruction on many data values simultaneously.
– Multiple Instruction/Multiple Data (MIMD) method: A
parallel-processing method that connects a number of
processors that run different programs or parts of a
program on different sets of data.
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Processor Speed
Determining Processor Speed
(Continued)
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Processor Speed
Determining Processor Speed
(Continued)
• Grid Computing: A process that harnesses idle
time on computers and then uses them to provide
processing for an application that needs more
speed and capability than may be available on a
single computer, or even on a supercomputer.
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