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Chapter 4

The Central Processor

and Memory

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The Central Processing Unit (CPU)Definition

• Central Processing Unit (CPU) or Processor:– executes program instructions and – performs the computer’s processing

actions.

• Integrated Circuits/Chip/Microchip: – 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– 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– oversees and controls all computer

activities• Instructions:

– Low level actions to be carried out during• input• processing• output• storage• transmission.

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The Central Processing Unit (CPU)Arithmetic/Logic Unit (ALU)

• Logical Operations:– Greater Than (>)– Less Than (<)– Equal To (=)

• Arithmetic Operations: – Addition– Subtraction– Multiplication– Division.

•Arithmetic Logic Unit (ALU):–part of the CPU –performs arithmetic and logical operations.

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MemoryDefinition

• Primary Storage• Primary Memory• Main Memory• Internal Memory• RAM:

– Primary memory holds data temporarily, – as the computer executes instructions.

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MemoryDefinition (Continued)

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MemoryMemory Size

• Bit: – On or Off– 1 or 0

• 2 Bits: – Four different values: 00, 01, 10, 11

• 3 Bits: – Eight different values:– 000, 001, 010, 011, 100, 101, 110, 111

• Byte: – 8 bits– 256 different values– Approximately 200 printable characters.

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MemoryMemory Size

• Kilobyte (KB or K): – 1000 bytes– 500 word text file about 3-4K

• Megabyte (MB): – One million bytes.– Bitmap 800 X 600 X 24 bits 1.4 MB

• Gigabyte (GB): – One billion bytes.

• Terabyte (TB):– One trillion bytes.

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MemoryMemory Size (Continued)

• How much space?– Turing

• 1,000 home directories• average home directory size 250 MB

– Image • 2400 X 1800 resolution • 64,000 colors

– Database• 500,000 people• first name• last name• phone number

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MemoryRAM and ROM

• ROM – Read-only Memory– Memory is persistent

even if computer is turned off

– Computer BIOS is stored on ROM chip

– BIOS (Basic Input Output System) need so computer can boot

• RAM – Random-access Memory– Read or Write– Memory is lost when

computer is turned off– Random-access any

part of the memory can be access in constant time.

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MemoryFlash Memory

• Flash Memory: – Read and Write– retains it contents even when electricity is

turned off.– Currently used in

• Cell phones• Digital Cameras• iPods, MP3 players• Key chains

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MemoryRAM, ROM and Flash Memory

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MemoryDefinition

• Boot: – To turn on the computer system– let the built-in self-test run.

• Cold Boot: – turned on from an off state– CPU invokes the ROM BIOS boot program, which 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 UnitDefinition

• Board: – A hardware device onto which chips and

their related circuitry are placed.

• System Board (Mother Board): – The hardware unit that houses a computer’s

processor, memory chips, ports, and add-in boards.

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Inside the System UnitProcessor 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 UnitEvolution of Intel Pentium Family of Microprocessors

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Inside the System UnitIntel Microprocessors

• Intel Celeron Processors– Does NOT have L2 cache, i.e., expensive

memory that speeds up performance• Intel Pentium Processors

– The Standard• Intel Xeon Processors

– Designed to work in pairs (dual processors)• Intel Itanium Processors

– 64-bit processor

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Inside the System UnitEvolution of Microprocessors for Macintosh Computers

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Inside the System UnitOther Microprocessor Chips

• AMD

• Digital Equipment Corp.

• Motorola

• MIPS Technologies

• Sun Microcomputers

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Inside the System UnitMemory 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 UnitPorts

• 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 UnitUniversal 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 UnitAdd-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 UnitPlug 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 SequenceThe Machine Cycle

• Machine Cycle: – The four processing steps: fetch, decode,

execute, and store.• Instruction Cycle (I-cycle):

– The first two steps (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 SequenceThe Machine Cycle

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The Processing SequenceRegisters

• Register: – temporary storage built into the processor– can move data and instructions more

quickly than main memory can• Four types:

– Storage Registers– Address Registers– Accumulators– General-Purpose Registers

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Processor SpeedDefinition

• 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 SpeedDefinition (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 SpeedDetermining Processor Speed

• Four elements: – System Clock– Bus Width– Word Size– Available Memory

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Processor SpeedDetermining 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 electric pulses per second.

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Processor SpeedDetermining 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 SpeedDetermining Processor Speed (Continued)

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Processor SpeedDetermining 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

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Processor SpeedDetermining Processor Speed (Continued)

• CISC: – Complex Instruction Set Computing– Intended to be an improvement– Complex instructions require main memory

• RISC:– Reduced Instruction Set Computing– A return to the old way– Compact instructions need only registers

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Processor SpeedDetermining 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 SpeedDetermining Processor Speed (Continued)

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Processor SpeedDetermining Processor Speed (Continued)

• Sequential Processing: – Processing in which the execution of one

instruction is followed by the execution of another.

• Parallel Processing: – For computers will multiple processor– computer handles different parts of a program

by executing instructions simultaneously.

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Processor SpeedDetermining Processor Speed (Continued)

• SIMD– Single Instruction/Multiple Data method– A parallel-processing method – executes the same instruction on many data

values simultaneously.• MIMD

– Multiple Instruction/Multiple Data method– A parallel-processing method– connects a number of processors that run

different programs or parts of a program on different sets of data.

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Processor SpeedDetermining Processor Speed (Continued)

• Grid Computing: – A process that harnesses idle time on a

computer– uses multiple computers to provide

processing for an application that needs more speed and capability