2.1Components of the CPU

2.12.1 Components of the CPUComponents of the CPUCentral Processing Unit (CPU) consists of

Control Unit

Arithmetic and Logic Unit

Registers

The components are connected by internal buses.

2.12.1 Components of the CPUComponents of the CPU

Control Unit (CU)“nerve centre” of CPU

send control signals to other components

sense their states to coordinate their operations

Arithmetic and Logic Unit (ALU)perform arithmetical, comparison and logical operation

work closely with the accumulation

2.12.1 Components of the CPUComponents of the CPU

Registerhigh-speed storage locations

temporarily hold data and instructions during processing

2.12.1 Components of the CPUComponents of the CPU

CPU

Machine CycleFetchDecodeExecute

2.12.1 Components of the CPUComponents of the CPU

CUALU

Memory Unit

(1) fetch

(2) decode(3) execute

Fetchingobtaining a program instruction or data item from memory

2.12.1 Components of the CPUComponents of the CPU

Decodingtranslating instructions into commands the computer can execute

2.12.1 Components of the CPUComponents of the CPU

Executingcarrying out the command

2.12.1 Components of the CPUComponents of the CPU

Storingwriting the result to the main memory

2.12.1 Components of the CPUComponents of the CPU

Determining factors of CPU performanceclock rate

word size

size of the cache

integrated circuit technology

2.22.2 Performance and Instruction Sets Performance and Instruction Sets of the CPUof the CPU

Clock ratenumber of pulses per second generated by an oscillator that sets the tempo for the CPU

measured in MHz or GHz

determine the number of executed instructions per second

not always directly proportional to its performance level

2.22.2 Performance and Instruction Sets Performance and Instruction Sets of the CPUof the CPU

Word sizenumber of bits the processor can interpret and execute at a given time

e.g. 64-bit processor manipulates 64 bits at a time

larger the word size, more data can be processed in the same amount of time

2.22.2 Performance and Instruction Sets Performance and Instruction Sets of the CPUof the CPU

Cachesmall amount of high-speed memory located inside or outside of the CPU

supply the processor with the most frequently requested data and instruction

2.22.2 Performance and Instruction Sets Performance and Instruction Sets of the CPUof the CPU

Integrated circuit technologysmaller process dimension smaller transistor gate lengths faster switching speed of transistor

2.22.2 Performance and Instruction Sets Performance and Instruction Sets of the CPUof the CPU

2.22.2 Performance and Instruction Sets Performance and Instruction Sets of the CPUof the CPU

Complex instruction set Simple instruction set

Longer instruction execution cycle

Allow each instruction to do more

Shorter instruction execution cycle

Allow each instructionto do less

Complex Instruction Set Computer (CISC)computers designed with full set of computer instructionsCISC CPU executes complex instruction more quickly than RISC CPUe.g. Intel Pentium microprocessors

2.22.2 Performance and Instruction Sets Performance and Instruction Sets of the CPUof the CPU

Reduced Instruction Set Computer (RISC)microprocessor designed to perform a smaller number of simple computer instructionsreduce instructions to those used more frequentlyRISC CPU executes simple instruction more quickly than CISC CPUe.g. PowerPC microprocessor

2.22.2 Performance and Instruction Sets Performance and Instruction Sets of the CPUof the CPU

Advanced technology used in CPUPipeliningSuperscalarParallel processing

2.22.2 Performance and Instruction Sets Performance and Instruction Sets of the CPUof the CPU

PipeliningCPU begins executing a second instruction before it completes the first instructionfaster processingeffective only if the CPU execute programs sequentially for most of the time

2.22.2 Performance and Instruction Sets Performance and Instruction Sets of the CPUof the CPU

2.22.2 Performance and Instruction Sets Performance and Instruction Sets of the CPUof the CPU

Fetch Decode Execute Fetch Decode Execute

Instruction 1 Instruction 2

Instruction flow without pipelining

2.22.2 Performance and Instruction Sets Performance and Instruction Sets of the CPUof the CPU

Fetch Decode Execute

Instruction flow with pipelining

Instruction 1

Instruction 2

Instruction 3

Superscalarpossible for executing more than one instruction at a time during a single clock cycle

Parallel Processingallocation of program execution to many execution units to execute more than one instruction in one cycle

2.22.2 Performance and Instruction Sets Performance and Instruction Sets of the CPUof the CPU

All the peripherals plug into the main board via various types of connector

Advantages of ATX main boardIntegrated I/O connectors

Reduced overlap between board and drivers

Reduced processor interference with add-on cards

User-friendly power connector

Better cooling conditions

2.32.3 Layouts of the Main BoardLayouts of the Main Board

2.32.3 Layouts of the Main BoardLayouts of the Main Board

PCI slots

BIOS

Battery

Floppy drive

IDE connectors

I/O connectors

Memory

Power supply connector

Southbridge

CPU socket

Northbridge

AGP slot

North Bridgecommunicate with CPU

control interaction with memory, PCI bus, Level 2 cache and AGP

communicate with the processor using Frontside Bus (FSB)

2.42.4 North Bridge / South BridgeNorth Bridge / South Bridge

South Bridgemanage the basic forms of input/output (USB, serial, audio, IDE, ISA)

2.42.4 North Bridge / South BridgeNorth Bridge / South Bridge

PCI (Peripheral Component Interconnect)

interconnection system between a CPU and attached devices

separate bus isolated from the CPU

use all active paths to transmit both address and data signals

2.52.5 I/O Expansion Slots of the Main I/O Expansion Slots of the Main BoardsBoards

PCI expansion slots

AGP (Accelerated Graphics Port)enable 3-D graphics to display quickly and smoothly on ordinary personal computers

useful in gaming, 3-D video, scientific graphic programs

intended exclusively for visual display devices

2.52.5 I/O Expansion Slots of the Main I/O Expansion Slots of the Main BoardsBoards

AGP slot

AGP (Accelerated Graphics Port)offer high-speed data transfer to and from RAM

optimize the use of memory

minimize the amount necessary for high-performance graphics

AGP data transfer rate is much greater than that of PCI video cards.

2.52.5 I/O Expansion Slots of the Main I/O Expansion Slots of the Main BoardsBoards

PCI and AGP

2.52.5 I/O Expansion Slots of the Main I/O Expansion Slots of the Main BoardsBoards

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