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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
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• 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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