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More on Computer Components

• Computer switches

• Binary number system

• Inside the CPU

• Cache memory

• Types of RAM

• Computer buses

• Creating faster CPUs

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Digital Data: Switches and Bits

• Electronic switches:– Vacuum tubes– Transistors– Integrated circuits

• Binary number system:– Representing numbers– Representing letters and symbols

• ASCII• Unicode

ON

OFF

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Electronic Switches

• Non-mechanical devices in computers that open and close circuits

• Types of electronic switches:– Vacuum tubes– Transistors:

• Semiconductors

– Integrated circuits

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• The on/off state of a switch represents one bit of data

• Bit (binary digit):– On = 1– Off = 0

OFF

Switches Representing Data

ON

0 1

OR = 1 bit

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The Binary Number System

100010x100

10010x10

1010x1

1

5 8 3 2

Base 10 10 digits 0 through 910 digits 0 through 964

2x3232

2x16162x8

82x4

42x2

22x1

1

• Number systems:– Organized ways to

represent numbersBinary 2 digits 0 and

1

89Base 10

=1 0 1 1 0 0 11 0 1 1 0 0 1

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Representing Letters and Symbols

A

ON

OFF

aBbC

• American Standard Code for Information Interchange (ASCII):– 8 bits equal 1 byte– 256 different combinations– 1 byte equals an alphanumeric character or symbol

• Unicode:– 16 bits equal 1 byte– 65000 different combinations– Used for all languages:

• English, Japanese, Chinese, etc. Click here to view an

ASCII Code chart

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The CPU: Processing Digital Information

• CPU components

• Types of CPUs

• What the CPU does:– Machine cycle:

• System clock• Cache memory

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The CPU

• Also known as a microprocessor or processor

• Executes instructions

• Components include:– Control unit– Arithmetic logic unit (ALU)– Registers– Cache memory

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Types of CPUsPROCESSOR MANUFACTURE

RTRANSISTOR

SCLOCK SPEED

Athlon XP AMD 54.3 million 2.20 GHz

Athlon 64FX AMD 106 million 2.4 GHz

Centrino Intel 77 million 1.70 GHz

Itanium 2 Intel 410 million 1.50 GHz

Pentium 4 Intel 55 million 3.20 GHz

Pentium 4 Processor-M

Intel 55 million 2.60 GHz

PowerPC G4 Motorola 57 million 1.00 GHz

PowerPC G5 IBM 58 million 2.00 GHz

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The CPU’s Machine Cycle• Also known as the processing cycle• Fetch:

– The Control Unit searches cache memory and then RAM for program instructions

– Instructions are moved to the Control Unit

• Decode:– The Control Unit reads and prepares the program instructions– The instructions are sent to the ALU

• Execute:– The ALU performs the calculations

• Store:– The results are stored in the registers

Click here to view the video “Inside the Chip” by Intel

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The System Clock

• Located on the motherboard

• Controls the CPU’s processing cycles

• Clock cycle:– Pulse or tick

• Clock speed:– Number of pulses per second– Measured in hertz (Hz)

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Cache Memory

• Small amount of memory located on the CPU chip or near it:– Level 1– Level 2

• Stores recent or frequently used instructions and data

• Used for quick access by the CPU

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RAM: The Next Level of Temporary Storage

• Dynamic RAM (DRAM):– Loses its electrical charge– Needs to be refreshed– SDRAM:

• Synchronous DRAM

– DDR SDRAM• Double data rate SDRAM

– RDRAM:• Rambus DRAM

• Static RAM (SRAM):– Does not lose its electrical charge– Faster than DRAM– Cache memory

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Memory and Size

• Data stored in bytes.

• Sizes:

• 1KB – 1 kilobyte means 1024 bytes

• 1MB – 1 Megabyte, approx. 1 million bytes

• 1GB – 1 Gigabyte, approx. a thousand MBs. (1,000,000,000 bytes)

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• Bus:– Electrical pathway used to move data

between components– Local bus:

• Connects the CPU with the memory

– Expansion bus:• Connects the CPU with peripheral devices

Buses: The CPU’s Data Highway

01100010

0111001101001000

00100111

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Bus Performance

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• Bus clock speed:– Rate of speed data moves from one location to

another– Measured in Mhz (millions of clock cycles per second)

• Bus width:– The number of bits of data moved on a bus at any one

time– Measured in bits:

• 16 bits• 32 bits

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Types of Expansion Buses

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• ISA and EISA:– Found on older computers– Connects mouse, modem, and sound card

• PCI:– Faster than ISA and EISA– Found on modern computers– Connects network, modem, and sound card

• AGP:– Used for three-dimensional graphics– Connects the graphics card and memory

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Making Computers Faster• Pipelining:

– The CPU processes more than one instruction at a time

Fetch Decode Execute

Store

Fetch Decode Execute

Store

Instruction 1

Instruction 2

Non-pipelined CPU

Fetch Decode Execute

Store

Fetch Decode Execute

Store

Fetch Decode Execute

Store

Fetch Decode Execute

Store

Instruction 1

Instruction 2

Instruction 3

Instruction 4

Pipelined CPU

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Making Computers Faster• Dual processing:

– Two CPUs on the same system

– Each processor shares the workload

• Parallel processing:– Network of computers– Each computer works

on a portion of the problem simultaneously

Dual processors

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