Computer Architecture2

 Computers are comprised of three things  The physical computer  The operating system  The user and programs running on the user’s behalf 3Computer Architecture

 Programmable machine designed to automatically carry out sequential operations  Basic functions  Input data  Process data  Output data  Store data (optional)  Is a calculator a computer??? 4Computer Architecture

1. Monitor (Visual display) 2. Motherboard 3. CPU 4. RAM 5. Expansion cards (maybe) 6. Power supply 7. Optical disc drive (maybe) 8. Hard disk drive 9. Keyboard 10. Mouse (or touch) 5Computer Architecture

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 Central Processing Unit (CPU)  Memory  Storage  Peripherals 7Computer Architecture

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 The CPU is the “core” of the computerCPU  Performs two basic operations  Arithmetic  Add, Subtract, Multiply, Divide, …  Logical  AND, OR, XOR, NOT, …  Does the same thing over and over  Fetch – get the next instruction from memory  Instruction is a sequence of bytes  Decode – determine what action the byte(s) specifies  Read – read required data from the memory address (optional)  Execute – carry out the encoded instruction  Fetch – Decode – Execute cycle can be used to implement any program 10Computer Architecture

 CPU executes the fetch–decode–execute cycle  When a program executes  Loads its instructions into memory from file  Tells the CPU the address of the first instruction  CPU keeps track of which memory location contains the next instruction  CPU fetches an instruction  CPU counter updates to the location of the next instruction Computer Architecture11

 The CPU performs the fetch-decode-execute cycle hundreds of millions of times per second  CPU’s “clock speed” tells you how many steps it can perform each second  1GHz clock speed translates into (roughly) one billion steps per second  Controlled by an oscillating crystal inside the CPU  Provides the “ticks” for the CPU clock 12Computer Architecture

 Physical device used to store data or programs  Two types  Volatile  Short-term memory  Requires power to maintain information  Random-access memory (RAM)  Non-volatile  Retains information when not powered  Generally used for long-term storage 13Computer Architecture

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 Non-volatile devices used to store data when the computer is not powered on  Magnetic  Floppy disk, magnetic tape, hard drives  Electromechanical  Paper tape, punched cards  Solid-state  EEPROM, Flash memory  Optical  CD, DVD, Blu-ray 15Computer Architecture

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 Storage devices retain information when powered off  Why bother with volatile memory?  Storage devices are MUCH slower than memory  Accessing the same data on a hard drive multiple time would slow down overall performance 17Computer Architecture

 Devices attached to a host computer  Not part of host’s core computer architecture  Expands host’s capabilities  Common peripherals  Input devices  Mouse, trackpad, scanners, audio input  Output devices  Displays, printers, speakers  Network cards  Storage 18Computer Architecture

 Fetch-Decode-Execute example  Find the following  Type and speed of CPU  Amount of RAM  Hard drive storage space 19Computer Architecture