11.1 The Components of a Computer System Unit

Power Supply Storage Devices Motherboard

Peripherals

11.1 The Components of a Computer System Unit

A case contains circuit boards, a power supply and storage devices

Main memory

Motherboard

CPU

Display card

DVD-ROM driveFloppy disk drive

Power supply

Hard disk drive

A system unit

11.1 The Components of a Computer Motherboard

The main circuit board in the system unit. Provide sockets for CPU, memory chips and expansion

slots. Contain circuitry that connects the components together.

11.1 The Components of a Computer Peripherals

Hardware devices connected to the system unit.

Broadband modem

Digital video

camera Printer Microphone

USB flash drive

Scanner

Peripherals

Monitor

SpeakerMouse

Keyboard

11.1 The Components of a Computer Peripherals

Hardware devices connected to the system unit.

Broadband modem

Digital video

camera Printer Microphone

USB flash drive

Scanner

Peripherals

Monitor

SpeakerMouse

Keyboard

11.2 Central Processing Unit (CPU) What is a CPU?

‘Brain’ of a computer. Executes the instructions of a computer program. Processes data to do a specific tasks. The processing power of the CPU usually determines the

overall performance of a computer. Most devices communicate with the CPU to carry out

certain tasks. CPU communicates with other devices through bus lines.

11.2 Central Processing Unit (CPU) What is a CPU?

The role of a CPU

11.2 Central Processing Unit (CPU) Major Components

Arithmetic and logic unit (ALU) Control unit (CU) Registers

11.2 Central Processing Unit (CPU) Arithmetic and Logic Unit (ALU)

Perform arithmetic and logical operations Use registers to hold data during calculations Results are usually stored in a register called an

accumulator

+

÷X

-

NOT

OR AND

11.2 Central Processing Unit (CPU) Control Unit (CU)

Keep track of the sequence of instructions being processed

Monitors and coordinates all I/O operations and system units

How the ALU and the CU execute an addition instruction

11.2 Central Processing Unit (CPU) Registers

Memory units inside a CPU. Provide storage space for ALU and CU. Small number of registers Fastest way for a CPU to access data Three types of register:

General purpose registers Control registers Status registers

11.2 Central Processing Unit (CPU) General Purpose registers (GPRs)

Mainly used by instructions of assembly and machine code programs.

Examples of general purpose registers: Accumulator(AX) Base register (BX) Counter (CX) Data register (DX)

11.2 Central Processing Unit (CPU) General Purpose registers (GPRs)

Functions of GPRs and the corresponding examples

FunctionExample of assembly instructions

Instruction Explanation

Load data from main memory into a register.

LOAD AX, 8 Store 8 in register AX.

Store data temporarily in arithmetic operations.

ADD BX, CXAdd the value stored in CX to that in BX, and store the sum in BX.

Store data from a register into main memory.

STORE ANS, AX

Store the data in register AX to the main memory address variable ANS.

11.2 Central Processing Unit (CPU) Control Registers

Provide temporary memory for CU to control the operation of instructions.

Major control registers: Instruction Register (IR) Program Counter (PC) Memory Address Register (MAR) Memory Data Register (MDR)

11.2 Central Processing Unit (CPU) Control Registers

Instruction Register (IR) Contains the instructions to be executed by the CPUs

Program Counter (PC) Contains the memory address of the next instruction to be

executed.

11.2 Central Processing Unit (CPU) Control Registers

Memory Address Register (MAR) and Memory Data Register (MDR)

Facilitate the communication of the CPU with the main memory through the system bus.

MAR holds the address of the memory location. MDR contains the data to be written into or read from the

location specified in MAR.

11.2 Central Processing Unit (CPU) Control Registers

1. Control unit issues a command to load the next instruction.

2. Control unit sends a READ control signal to the main memory via the control bus

3. PC copies the address of the required instruction to MAR.

4. MAR passes the address to the main memory via the address bus.

5. The main memory returns the addressed data to MDR via the data bus.

6. The instruction in MDR is then loaded into IR for execution.

Execution process of program instructions

11.2 Central Processing Unit (CPU) Status Registers

Contain a number of flag bits indicating the status after the execution of instructions

Used in instructions of conditional testing and program branching

11.2 Central Processing Unit (CPU) Status Registers

Essential flags in the status register of CPU 8088

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

Zero flag (Z): Set to 1 if the evaluated result is zero; set to 0 otherwise.Sign flag (S): Set to 1 if the evaluated result is negative; set to 0 otherwise.Parity flag (P): Set to 1 if the evaluated result is an odd parity.Carry flag (C): Set to 1 if the evaluated result contains a carry; set to 0 otherwise.Overflow flag (O): Set to 1 if the evaluated result has overflowed. (i.e. the resulting value is too large to be stored in the memory unit)

O S Z P C

11.2 Central Processing Unit (CPU) System Bus

Also know as bus line Physical wiring that connects the various components of

a computer system Transmit data between the CPU and other components

Bus type Function

Data bus Transfer data and instructions.

Address bus

Transfer the source address or the destination address of data.

Control bus

Indicate the direction of the data transfer and coordinate thetiming of the event during transfer.

Functions of data bus, address bus and control bus

11.2 Central Processing Unit (CPU) System Bus

Size of a bus = bus width Bus width determines the number of bits of data the

computer can transmit at one time.

System Bus

System Bus

11.2 Central Processing Unit (CPU) System Bus

Interconnection of computer units by system bus

11.2 Central Processing Unit (CPU) System Bus

Model of CPU Bus width

Intel 8088 8-bit

Intel 80286 16-bit

Intel 80486 32-bit

Pentium 64-bit

Intel Core 2 Duo 64-bit

Bus width among different CPUs

11.2 Central Processing Unit (CPU) System Bus

Model of CPU Bus width

Intel 8088 8-bit

Intel 80286 16-bit

Intel 80486 32-bit

Pentium 64-bit

Intel Core 2 Duo 64-bit

Bus width among different CPUs

11.3 Machine Cycle

Machine Cycle Process of executing an instruction in a CPU

Sub-cycle Description

FetchRead the next instruction from the main memory into instruction register (IR).

DecodeIdentify the operation code and operands in an instruction.

ExecuteInterpret the operation code and perform the required operation.

Sub-cycles of a machine cycle

11.3 Machine Cycle

Machine Cycle

Process of a machine cycle

11.3 Machine Cycle

Machine Cycle Interrupt Sub-cycle

At the end of the execution of an instruction, the CPU detects whether an interrupt has occurred.

If have interrupt

Interrupt served

CPU resumes the operation of

the next instruction of

the active process

End of execution of an instruction

1. CPU saves the current process status

2. Handles the interrupt immediately

11.3 Machine Cycle

Machine Cycle Interrupt Sub-cycle

At the end of the execution of an instruction, the CPU detects whether an interrupt has occurred.

If have interrupt

Interrupt served

CPU resumes the operation of

the next instruction of

the active process

End of execution of an instruction

1. CPU saves the current process status

2. Handles the interrupt immediately

11.4 Measurement of CPU Speed Clock Rate

Measure speed of CPU Measurement unit: megahertz (MHz) or gigahertz (GHz) 1 hertz = 1 clock cycle per second

Model of CPU

Years of production

Typical clock rate

Duration of one clock cycle

Intel 8088 1979 – 1982 4.77 MHz 0.21μs (210 ns)

Intel 80286 1982 – 1986 6 MHz – 25 MHz 40 ns – 166.7 ns

Intel 80386 1986 – 2007 16 MHz – 40 MHz 25 ns – 62.5 ns

Intel 80486 1989 – 2007 16 MHz – 100 MHz

10 ns – 33.4 ns

Pentium 1993 – 1996 60 MHz – 200 MHz

5 ns – 16.7 ns

Pentium II 1997 – 1999 233 MHz – 450 MHz

2.2 ns – 4.3 ns

Pentium III 1999 – 2001 500 MHz – 1.13 GHz

885 ps – 2 ns

Pentium IV 2000 – now 1.4 GHz – 3.4 GHz 294 ps – 714 ps

Intel Core 2 Duo

2000 – now 1.06 GHz – 3 GHz 333 ps – 943 ps

Clock rates of popular CPUs for the past thirty years

11.4 Measurement of CPU Speed Word Length

Number of bits of data and instructions the CPU can handle at one time

Advantage of longer word length: More data can be processed in one time. More instructions can be included in the instruction

set. More complicated instructions can be included in the

instruction set.

A 64-bit CPU

11.4 Measurement of CPU Speed Word Length

Number of bits of data and instructions the CPU can handle at one time.

Advantage of longer word length: More data can be processed in one time. More instructions can be included in the instruction

set. More complicated instructions can be included in the

instruction set.

A 64-bit CPU

11.5 Main Memory

Main Memory Accessible to the CPU of a computer without using other

I/O channels. The memory chips are installed on the motherboard. Used to store data Used to store instructions that CPU will execute 2 major types:

Random access memory (RAM) Read-only memory (ROM)

11.5 Main Memory

Random Access Memory (RAM) Temporarily hold the data and instructions of application

software and the operation system Volatile = all data stored in RAM disappears instantly

after the computer is turned off Access time is just a hundredth of hard disk Measurement units: bytes (B), kilobytes (KB), megabytes

(MB), gigabytes (GB), terabytes (TB)

A RAM module

11.5 Main Memory

Random Access Memory (RAM) Two main streams:

Dynamic random access memory (DRAM) Static random access memory (SRAM)

DRAM SRAM

Speed (clock rate) Lower Higher

Cost Lower Higher

Power consumption

Higher than SRMA Lower than DRAM

Storage capacity Larger Smaller

ApplicationComputer main memory, game console

CPU cache, hard disk buffer, printer buffer, PDA

Characteristics of DRAM and SRAM

11.5 Main Memory

Read-only Memory (ROM) Store the permanent information supplied by the

manufacturer Contain the bootstrap program which loads and initializes

the operation system of the computer. Store basic input/output system (BIOS) Non-volatile Variants of ROM:

Erasable programmable ROM (EPROM) Electrically erasable programmable ROM

(EEPROM)

A ROM chip installed on a motherboard

11.5 Main Memory

Cache Memory High-speed memory Store data and instructions that have been recently used

by the CPU Integrated into a CPU or resided close to a CPU

CPU requests an instruction or data

Searches cache memory first in a very short time

Acquires the data and proceeds to the next task

Look up in the main memory

Found

Not found

11.5 Main Memory

Cache Memory High-speed memory Store data and instructions that have been recently used

by the CPU Integrated into a CPU or resided close to a CPU

CPU requests an instruction or data

Searches cache memory first in a very short time

Acquires the data and proceeds to the next task

Look up in the main memory

Found

Not found

11.6 Latest Development of CPU and Main Memory

Latest Technology of CPU The future development of the CPU in the future has

focused on the integration of more cores into the CPU.

Processors on an Intel 45nm wafer photographed with a pencil. Each dual core chip consists of 410 million transistors.

11.6 Latest Development of CPU and Main Memory

Latest Technology of CPU Smaller chip die Parallel processing of multiple cores Better pipelining technology Take full advantage of the newly developed high speed

Double-Data-Rate 3 (DDR3) SDRAM Shortened the speed gap between the CPU and main

memory

AMD Phenom Quad-Core Processor Die

Intel 45nm quad-core processor and its chip die

11.6 Latest Development of CPU and Main Memory

Latest Technology of Main Memory The new standard of main memory module is known as

Double-Data-Rate 3 (DDR3) SDRAM. DDR3 operates at a lower voltage level but higher

frequency than its predecessor Popular in high-end computer market and notebook

computers

DDR3 memory modules

11.6 Latest Development of CPU and Main Memory

Latest Technology of Main Memory The new standard of main memory module is known as

Double-Data-Rate 3 (DDR3) SDRAM. DDR3 operates at a lower voltage level but higher

frequency than its predecessor Popular in high-end computer market and notebook

computers

DDR3 memory modules