Intro to Computer Technology: System Unit - Lecture 2 PDF

Lecture 2 The System Unit: Processing and Memory  Data and Program Representation In order to be understood by a computer, data and programs need to be represented appropriately. Coding systems: Used to represent data and programs in a manner understood by the computer. Dig...

Lecture 2 The System Unit: Processing and Memory  Data and Program Representation In order to be understood by a computer, data and programs need to be represented appropriately. Coding systems: Used to represent data and programs in a manner understood by the computer. Digital computers: Can only understand two states, off and on (0 and 1). Digital data representation: The process of representing data in digital form so it can be understood by a computer. 2  Digital Data Representation Bit: The smallest unit of data that a binary computer can recognize (a single 1 or 0) Byte = 8 bits Byte terminology used to express the size of documents and other files, programs, etc. Prefixes are often used to express larger quantities of bytes: kilobyte (KB), megabyte (MB), gigabyte (GB), terabyte (TB), petabyte (PB), exabyte (EB), zettabyte (ZB), yottabyte (YB). 3  Data and Program Representation Representing Numerical Data Representing Numerical Data: The Binary Numbering System – Numbering system A way of representing numbers – Decimal numbering system Uses 10 symbols (0-9) – Binary numbering system Uses only two symbols (1 and 0) to represent all possible numbers – In both systems, the position of the digits determines the power to which the base number (such as 10 or 2) is raised 4  Coding Systems for Text-Based Data ASCII (American Standard Code for Information Interchange): coding system traditionally used with personal computers 5 Inside the System Unit 6  Basic Computer Hardware components Computer chip: A very small pieces of silicon or other semi-conducting material onto which integrated circuits are embedded Circuit board: A thin board containing computer chips and other electronic components Motherboard or system board: The main circuit board inside the system unit – All devices must connect to the motherboard – External devices (monitors, keyboards, mice, printers) typically connect by plugging into a port exposed through the exterior of the system unit – Wireless devices connect through a transceiver or wireless networking technology (like Bluetooth) 7 Ports Plugs  The CPU Central processing unit (CPU): circuitry and components packaged together and connected directly to the motherboard – Does the vast majority of processing for a computer – Also called a processor; called a microprocessor when talking about personal computers Dual-core CPU: Contains the processing components (cores) of two separate processors on a single CPU Quad-core CPU: Contains 4 cores Typically different CPUs for desktop computers, portable computers, servers, mobile devices, consumer devices, etc. Often made by Intel or AMD 10 The CPU 11 The CPU 12  Bus Width, Bus Speed, and Bandwidth Bus: An electronic path over which data can travel Bus width: The number of wires in the bus over which data can travel Bus width and speed determine the throughput (or bandwidth) of the bus – The amount of data that can be transferred by the bus in a given time period 13  Word Size and Cache Memory Word size: The amount of data that a CPU can manipulate at one time – Typically 32 or 64 bits Cache memory: Special group of very fast memory chips located on or close to the CPU – Level 1 is fastest, then Level 2, then Level 3 – More cache memory typically means faster processing – Usually internal cache (built into the CPU) – Often some cache dedicated to each core; may also have some shared cache accessible by any core 14  Memory Memory refers to chip based storage RAM (random access memory): Computer’s main memory – Consists of chips arrange on a circuit board called a memory module plugged into the motherboard – Stores essential parts of operating system, programs, and data the computer is currently using – Adequate RAM is needed to run programs – Volatile: Contents of RAM is lost when the computer is shut off – Most personal computers use SD-RAM (Synchronous dynamic random-access memory) – MRAM and PRAM: non-volatile RAM under development 15  Inside the System Unit Each location in memory has an address – Each location typically holds one byte – Computer system sets up and maintains directory tables to facilitate retrieval of the data 16  Memory Registers: High-speed memory built into the CPU; used by the CPU ROM (read-only memory): Non-volatile chips located on the motherboard into which data or programs have been permanently stored – Retrieved by the computer when needed – Being replaced with flash memory for firmware Flash memory: Type of nonvolatile memory that can be erased and reprogrammed – Some flash memory chips are used by the computer – Flash memory chips are also used in flash memory storage media (sticks, cards, and drives) 17  Quick Quiz 1. Which type of memory is erased when the power goes out? a. ROM b. RAM c. flash memory 2. True or False: The CPU can also be called the motherboard. 3. A(n) electronic path within a computer over which data travels is called a(n) _____________. Answers: 1) b; 2) False; 3) bus 19  How the CPU Works CPU: Consists of a variety of circuitry and components packaged together – Transistor: Key element of the microprocessor Made of semi-conductor material that acts like a switch controlling the flow of electrons inside a chip Today’s CPUs contain hundreds of millions of transistors; the number doubles about every 18 months (Moore’s Law) Transistor 20 Typical CPU Components 21  How the CPU Works Typical CPU Components – Arithmetic/Logic Unit (ALU) Performs arithmetic involving integers and logical operations – Floating Point Unit (FPU) Performs decimal arithmetic – Control Unit Coordinates and controls activities within a CPU core – Prefetch Unit Attempts to retrieve data and instructions before they are needed for processing in order to avoid delays 22  How the CPU Works – Decode Unit Translates instructions from the Pre-fetch unit so they are understood by the control unit, ALU, and FPU – Registers and Internal Cache Memory Store data and instructions needed by the CPU – Bus Interface Unit Allows the core to communicate with other CPU components 23  The System Clock and the Machine Cycle Machine cycle: The series of operations involved in the execution of a single machine level instruction – Fetch: The program instruction is fetched – Decode: The instructions are decoded so the control unit, ALU, and FPU (Floating-Point Unit )can understand them – Execute: The instructions are carried out – Store: The original data or the result from the ALU or FPU execution is stored in the CPU’s registers 24  Processing Speed CPU clock speed: One measurement of processing speed – Measured in megahertz (MHz) or gigahertz (GHz) – Higher CPU clock speed = more instructions processed per second Other factors (CPU architecture, memory, bus speed, amount of RAM, etc.) also affect the overall processing speed of a computer Benchmark tests: Can be used to evaluate overall processing speed 25  The System Clock and the Machine Cycle System clock: Timing mechanism within the computer system that synchronizes the computer’s operations – Each signal is a cycle – Number of cycles per second = hertz (Hz) – Many PC system clocks run at 200 MHz – Computers can run at a multiple or fraction of the system clock For instance, with a CPU clock speed of 2 GHz, the CPU clock “ticks” 10 times during each system clock tick – During each CPU clock tick, one or more pieces of microcode are processed 26 Pipelining 27  Making Computers Faster and Better Now and in the Future – Pipelining Allows multiple instructions to be processed at one time – Multiprocessing and Parallel Processing Use multiple processors to speed up processing 28  Future Trends Nanotechnology: The science of creating tiny computers and components less than 100 nanometers in size Future applications may be built by working at the individual atomic and molecular levels Optical computer: Uses light, such as from laser beams or infrared beams, to perform digital computations Cloud Computing 29