Chapter 4
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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)
• Arithmetic Logic Unit (ALU):
– part of the CPU
– performs arithmetic and logical operations.
• Logical Operations:
– Greater Than (>)
– Less Than (<)
– Equal To (=)
• Arithmetic Operations:
– Addition
– Subtraction
– Multiplication
– Division.
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Memory
Definition
• Primary Storage
• Primary Memory
• Main Memory
• Internal Memory
• RAM:
– Primary memory holds data temporarily,
– as the computer executes instructions.
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Memory
Definition (Continued)
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Memory
Memory 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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Memory
Memory 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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Memory
Memory 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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Memory
RAM and ROM
• ROM
– Computer BIOS is stored on ROM chip
– BIOS (Basic Input Output
System) need so computer can boot
• RAM
– Read-only Memory
– Memory is persistent even if computer is turned off
–
–
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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Memory
Flash 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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Memory
RAM, ROM and Flash Memory
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Memory
Definition
• 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 Unit
Definition
• 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 Unit
Processor 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 Unit
Evolution of Intel Pentium Family of
Microprocessors
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Inside the System Unit
Intel 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 Unit
Evolution of Microprocessors for
Macintosh Computers
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Inside the System Unit
Other Microprocessor Chips
• AMD
• Digital Equipment Corp.
• Motorola
• MIPS Technologies
• Sun Microcomputers
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Inside the System Unit
Memory 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 Unit
Ports
• 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 Unit
Universal 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 Unit
Add-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 Unit
Plug 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 Sequence
The 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 Sequence
The Machine Cycle
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The Processing Sequence
Registers
• 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 Speed
Definition
• 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 Speed
Definition (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 Speed
Determining Processor Speed
• Four elements:
– System Clock
– Bus Width
– Word Size
– Available Memory
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Processor Speed
Determining 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 Speed
Determining 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 Speed
Determining Processor Speed
(Continued)
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Processor Speed
Determining 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 Speed
Determining 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 Speed
Determining 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 Speed
Determining Processor Speed
(Continued)
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Processor Speed
Determining 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 Speed
Determining 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 Speed
Determining 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
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