CPU Architecture

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CPU Architecture

• Gani Nashi
• West Herts College

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CPU Components

• Core
• Math Co-processor
• Instruction sets / Microcode
• Multimedia extensions
• Registers
• Flags
• Pipelining
• Cache

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Pentium Architecture
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Arithmetic Logic Unit (ALU)

• The part of the central processing unit that
  deals with operations such as addition,
  subtraction, and multiplication of integers and
  Boolean operations. It receives control signals
  from the control unit telling it to carry out
  these operations.

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Arithmetic Logic Unit (ALU)

• Addition and subtraction
• Multiplication and division
• Logical tests
• Comparison
• Bit shifting

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Control Unit (CU)

• This controls the movement of instructions in and
  out of the processor, and also controls the
  operation of the ALU. It consists of a decoder,
  control logic circuits, and a clock to ensure
  everything happens at the correct time. It is
  also responsible for performing the instruction
  execution cycle.

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Control Unit

• Decoder
• Timer or clock
• Control logic circuits

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Register Array

• This is a small amount of internal memory that is
  used for the quick storage and retreival of data
  and instructions. All processors include some
  common registers used for specific functions,
  namely the program counter, instruction register,
  accumulator, memory address register and stack
  pointer.

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Registers

• Program Counter (PC)
• Instruction Register (IR)
• Accumulator (A, or ACC)
• Memory Address Register (MAR)
• Memory Buffer Register (MBR)
• Flag register / status flags
• Other general purpose registers

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BUS Description

• The system bus is a cable which carries data
  communication between the major components of the
  computer, including the microprocessor
• The system bus consists of three different groups
  of wiring, called the data bus, control bus and
  address bus. These all have separate
  responsibilities and characteristics, which can
  be outlined as follows

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Control Bus

• The control bus carries the signals relating to
  the control and co-ordination of the various
  activities across the computer, which can be sent
  from the control unit within the CPU.
• Different architectures result in differing
  number of lines of wire within the control bus,
  as each line is used to perform a specific task

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Data Bus

• This is used for the exchange of data between the
  processor, memory and peripherals, and is
  bi-directional so that it allows data flow in
  both directions along the wires. Again, the
  number of wires used in the data bus (sometimes
  known as the 'width') can differ.

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Address Bus

• The address bus contains the connections between
  the microprocessor and memory that carry the
  signals relating to the addresses which the CPU
  is processing at that time, such as the locations
  that the CPU is reading from or writing to.

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Logic Gates
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Introduction

• Logic gates are the basic components in digital
  electronics. They are used to create digital
  circuits and even complex integrated circuits.
  For example, complex integrated circuits may
  bring already a complete circuit ready to be used
  microprocessors and microcontrollers are the
  best example but inside them they were
  projected using several logic gates.

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Inverter

• As the name implies, inverter will invert the
  number entered. If you enter 0, you will get a
  1 on its output, and if you enter a 1, you
  will get a 0 on its output. Inverter gate is
  also known as NOT and its output is Y /A.

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Inverter Output
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Integrated circuit 7404
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AND

• As its name implies, an AND logic gate performs
  an AND logic operation, which is a
  multiplication. It has at least two inputs. So,
  if A and B are its inputs, at the output we will
  find A x B (also represented as A B). So, AND
  logic gate can be summarized by the formula Y A
  x B (or Y A B).

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AND logic gate
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AND Table
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Expanding AND inputs
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7408 integrated circuit
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NAND

• The N letter on NAND stands for NOT, meaning
  that NAND logic gate is an AND gate with an
  inverter attached. So, its output is the opposite
  from AND. Its symbol is the same of AND but with
  a o on its output, meaning that the output is
  inverted. You can build yourself a NAND gate by
  connecting an AND gate to an inverter.

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NAND logic gate
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NAND Table
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OR

• As its name implies, an OR logic gate performs an
  OR logic operation, which is an addition. It
  has at least two inputs. So, if A and B are its
  inputs, at the output we will find A B. So, OR
  logic gate can be summarized by the formula Y A
  B.

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OR logic gate
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OR Table
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Expanding OR
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NOR

• The N letter on NOR stands for NOT, meaning
  that NOR logic gate is an OR gate with an
  inverter attached. So, its output is the opposite
  from OR. Its symbol is the same of OR but with a
  o on its output, meaning that the output is
  inverted. You can build yourself a NOR gate by
  connecting an OR gate to an inverter.

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NOR logic gate
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NOR Table
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XOR

• XOR stands for exclusive OR. XOR gate compares
  two values and if they are different its output
  will be 1. XOR operation is represented by the
  symbol Å. So Y A Å B.

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XOR logic gate
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XOR Table
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Expanding XOR inputs

• you will need to add an OR gate

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XNOR

• XNOR stands for exclusive NOR and is an XOR gate
  with its output inverted. So, its output is at
  1 when the inputs have the same value and 0
  when they are different. XNOR operation is
  represented by the symbol (). So Y A () B

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XNOR logic gate
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XNOR Table