ObjectivesObjectives (continued)Objectives (continued)Why You Need to Know About...Computer ArchitectureInside the BoxThe CPUThe CPU (continued)How Transistors WorkDigital Logic CircuitsDigital Logic Circuits (continued)The Basic Boolean OperatorsThe Basic Boolean Operators (continued)The Basic Boolean Operators (continued)Digital Building BlocksDigital Building Blocks (continued)Digital Building Blocks (continued)Digital Building Blocks (continued)Digital Building Blocks (continued)Digital Building Blocks (continued)Digital Building Blocks (continued)Gate BehaviorComplex CircuitsComplex Circuits (continued)Complex Circuits (continued)Complex Circuits (continued)Complex Circuits (continued)Complex Circuits (continued)Von Neumann ArchitectureVon Neumann Architecture (continued)Von Neumann Architecture(continued)Von Neumann Architecture(continued)BusesPeripheral BusesStorageMemoryMemory (continued)Mass StorageMass Storage (continued)Mass Storage (continued)Mass Storage (continued)Input/Output SystemsInput DevicesOutput DevicesOutput Devices (continued)Interrupts and PollingChoosing the Best Computer HardwareOne Last ThoughtSummarySummary (continued)Summary (continued)Connecting with Computer Science2Objectives• Learn why you need to understand how computers work• Learn what a CPU is, and what it is made of• Learn how digital logic circuits are constructed• Learn the basic Boolean operators• Understand how the basic logic gates operate and are used to build complex computer circuitsConnecting with Computer Science3Objectives (continued)• Learn the importance of von Neumann architecture• Understand how the computer uses memory• Learn what a system bus is and what its purpose is• Understand the difference between memory and storageConnecting with Computer Science4Objectives (continued)• Be able to describe basic input/output devices• Understand how a computer uses interrupts and pollingConnecting with Computer Science5Why You Need to Know About...Computer Architecture• Computer: hardware designed to run software– Purpose: accomplish desired tasks• Professional’s need: understand logical connection between hardware and software • Computer architecture: organization of hardware components into a computer systemConnecting with Computer Science6Inside the Box• Computer system: an external view– Monitor – Keyboard and mouse – Computer case • CPU (central processing unit)– Resides in case on main board or motherboard– Computational center served by all other parts– Touch point for the study of computer architectureConnecting with Computer Science7Connecting with Computer Science8Connecting with Computer Science9The CPU• The CPU is the computer– Contains digital components that do processing– Fundamental component: transistor• Transistor – Electronic switch accommodates binary values – Millions of transistors per chip– Organized into a higher level called a circuitConnecting with Computer Science10The CPU (continued)• Four basic functions: Adding, Decoding, Shifting, Storing• Four corresponding transistor circuits– Adder: adds, subtracts, multiplies, divides– Decoder: reacts to specific bit patterns – Shifter: moves bits to right or left– Flip-flops (latches): used to store memory bitsConnecting with Computer Science11How Transistors Work• Material composition: silicon or germanium• Logically organized into three parts: emitter, collector, and base• Transistor as electronic switch– Base used to turn current on and off– Capacity to control current translates into capacity to manipulate binary values of 1 and 0• Size considerations: Typical transistor 130 nanometers wide (Pentium IV)Connecting with Computer Science12Connecting with Computer Science13Digital Logic Circuits• Logic circuit– Next level of organization above transistor– Leverages switching function of transistor– Performs operations of Boolean algebra• Boolean algebra– Functions relating binary input and output– Chief operators: AND, OR, NOT– Boolean variables are true (1) or false (0)– Boolean expressions use Boolean operators and variablesConnecting with Computer Science14Digital Logic Circuits (continued)• Truth tables – Convenient tabular representations of Boolean expressions– Column(s) represent inputs and output(s)– Rows correspond to each possible combination of inputs • 2n rows needed for n inputs (n is positive integer)• Example: two inputs require 22= 4 rowsConnecting with Computer Science15The Basic Boolean Operators• Three Basic Operators: AND, OR, NOT• AND operator – Takes two values as input (x and y) and generates one output (z)– Both inputs must be true (1) for output to be true (1)• When x = 1 and y = 1, z = 1– Any other combination yields output of false (0) – Equivalent Boolean Expression: xy = zConnecting with Computer Science16Connecting with Computer Science17The Basic Boolean Operators (continued)• OR operator– Takes two values as input (x and y) and generates one output (z)– Either input valued true (1) will cause output to be valued true (1)– When both inputs are valued false (0), output will be valued false (0) – Equivalent Boolean expression: x + y = zConnecting with Computer Science18Connecting with Computer Science19The Basic Boolean Operators (continued)• NOT operator– Takes one value as input (x) and generates one output (z)– Reverses value of input.• When x = 1, z = 0 • When x = 0, z = 1 Equivalent Boolean expression: x′ = z or x = z xConnecting with Computer Science20Connecting with Computer Science21Digital Building Blocks• Circuit Hierarchy– Gates: transistor circuits implement Boolean operators– Gates grouped into more complex circuits that carry out computer tasks• Reliability– Binary values maintained with consistent voltage levels – Output of gates completely determined by input• Six fundamental gates– AND, OR, NOT (primitive or basic) – NAND, NOR, XOR (constructed from AND, OR, NOT)Connecting with Computer Science22Digital Building Blocks (continued)• AND gate– Allows for two inputs and has one output– Truth table identical to that of AND Boolean OperatorConnecting with Computer Science23Digital Building Blocks (continued)• OR gate– Allows for two inputs and has one output– Truth table identical to that of Boolean ORConnecting with Computer Science24Digital Building
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