CMSC 1041 Machine Architecture An Introduction to Computer Components

CMSC 1042 Major Computer Components l Central Processing Unit (CPU) l Bus l Main Memory (RAM) l Secondary Storage l I / O Devices l Starting the computer

CMSC 1043 Computer Functional Diagram

CMSC 1044 CPU l Central Processing Unit l The “brain” l Controls all other computer functions

CMSC 1045 CPU (Continued) l Types oIntel: 4004, 8008, 8080, 8086, 80186, 80286, 80386, 80486, Pentium, Merced, ? oMotorola: 6800, 6809, 68000, 68020, 68040, 68060, 68080, RISC, ? oDEC: PDP-8/10/11, VAX, Alpha, ARM, ? oAMD: K4, K5, K6, K7, ? oZilog: Z80, Z800, Z8000 (Still around?)

CMSC 1046 CPU (Continued) Just a collection of fast ON/OFF switches Forty-million transistors in this space (or less)

CMSC 1047 CPU (Continued) l Some MainFrame CPUs are limited by the speed of light.

CMSC 1048 The Buss l Different major components are connected by the buss. l A buss is a group of parallel wires (or circuit-board connections) that carry control signals and data between components.

CMSC 1049 Main Memory l l Main memory is made up of two-state devices. l l Two state devices have just two possible states (Wow!). An ON/OFF switch is a two-state device. l l In memory, one state stands for 1, the other for 0.

CMSC Main Memory (Continued) l l Memory can hold any type of data that can be represented by a combination of two states --- and only those types. l l Examples: l l 1 = yes, 0 = no l l 01 = Red, 10 = Blue, 11 = Green l l 00 = 0, 01 = 1, 10 = 2, 11 = 3

CMSC Main Memory (Continued) l l Memory often made up of capacitors (electron storage devices). l l “Charged” (“full”) 1, ON, SET. l l “Discharged” (“empty”) 0, OFF, RESET, CLEARED

CMSC Main Memory (Continued) “The Incredible Shrinking Capacitor” l Technology is constantly improving oExperience smarter engineers oSmarter engineers smaller devices oSmaller devices cheaper systems oCheaper systems more sales oMore sales more experience

CMSC Main Memory (Continued) “The Incredible Shrinking Capacitor” l Memory chips now routinely contain 128x2 20 (“128 Meg”) bits. l “If car-makers built cars the way chip- makers build chips, we’d all drive Mercedes-Benzs that cost $4.95, got 1000 miles to the gallon, and fit in our pockets when we got to our destination.”

CMSC Main Memory ((still) Continued) l l Memory is divided into cells, where each cell contains 8 bits. Remember that 8 bits is called a byte. l l Each of these cells are numbered. The number is the cell’s address. l l The address is the, um, ah, er, well the “address” we use to specify which byte we want to work with.

CMSC Main Memory “Nepenthe: Elixir of Forgetfulness.” l Main memory is volatile (it goes away when you turn off the power). l Capacitors leak charge goes away data is lost. l “If car-makers … and they would disappear as soon as we turned off the engine.” l There are non-volatile memory systems.

CMSC Main Memory Reading & Writing (for ‘rithmetic) l l In addition to the circuitry that holds the bits, there are other circuits that: o oGet the value of the data held at a particular address --- READ. o oStore data at particular address --- WRITE. o oSome memory is designed so that it cannot be written Read-Only Memory ROM o oMany types of ROM are non-volatile.

CMSC Memory Access l l Memory at all addresses can be accessed in the same amount of time. l l Memory can be accessed in any order, like cuts on a CD (not “Byte 0, Byte 1, Byte 3, …, Byte N ” like cuts on a tape). l l Access in any order Random Access Random Access Memory RAM

CMSC Secondary Storage l Many Types: oDisks (Random Access) oTapes (Sequential access) l Persistent storage (Stays when the power goes off) oPrograms oData files (binary, text) oSystem organization (Directory structure)

CMSC I/O l Converts some “real” thing (sound, movement, electrical signal) into bits. l Usually done by specialized “add ons” oKeyboard oMonitor oSoundcard l Sometimes disk and tape drives are considered I/O devices.

CMSC Computer/Peripheral Communication “There be Dragons and Mysteries in these Waters.” l Ports oElectronic connections through which data can enter or leave the computer oIdentified by port numbers (like memory cells are identified by addresses) oUsually each device (keyboard, soundcard, network card, modem) with be assigned to exclusive use of one or more ports

CMSC Computer/Peripheral Communication Doesn’t everyone speak Latin ? l l I/O devices normally exchange two things with the computer l l “Data” --- e.g. bits to and from a modem --- this is what you want l l “Protocol” --- coordination between the computer and the device to insure the data is transmitted correctly --- you don’t see it and you don’t want to.

CMSC Computer/Peripheral Communication “No thanks, I peel my own.” l l Protocol insures that the device and the computer “speak the same language.” l l Parity (must there be an even number of bits per exchange?) l l “Endedness” (some computers transmit numbers from-left-to-right, others from-right-to-left)

CMSC Computer/Peripheral Communication “Let’s not both talk at once” l l Usually duplex (two-way) rather than simplex (one-way) l l Simplex: mail, TV/Radio broadcast. o oHalf-duplex: two-way communication, but in communication can occur only in one direction at a time (polite telephone call). o oFull-duplex - allows communication in both directions at the same time.

CMSC Computer/Peripheral Communication Controllers l l Special-purpose “CPUs” designed to handle I/O l l Free main CPU by taking over comms tasks. l l Allow more complex I/O, more devices l l So effective that many machines are designed to use controllers even if only one device is connected to a port.

CMSC Computer/Peripheral Communication Parallel and Serial Communication l l Parallel - All the bits of a pattern are transferred at the same time, with each bit being transferred on a separate line. Requires multi-wire cables. “Gimme Five!” l l Serial - Transmits one bit at a time. Slower, but uses a simpler data path. “Here’s one bit, here’s another bit …”

CMSC Bits, Bytes and Words l A bit is a single 1 or 0; a single choice l A byte is 8 bits oA word is 16 bits or 2 bytes oLong word = 4 bytes = 32 bits oQuad word = 8 bytes = 64 bits oProgramming languages may use these terms when organizing data l A is 4 bits?? (It’s a small byte.)

CMSC More Bits and Bytes l There are 16-, 32-, and 64-bit machines l All of UMBC Unix systems are 32-bits

CMSC Booting the Computer l It refers to the computers start-up procedure. l Comes from the expression “pulling yourself up by your bootstraps” l Starts with instructions stored in the ROM chips. (Why: two reasons.)

CMSC Booting the Computer (continued) l A typical boot sequence: oTest critical components (and maybe all components). oTurn on and setup critical devices (console, keyboard, power monitor, operating system storage media) oLoad operating system (usually from disk) oTransfer control to operating system.

CMSC Booting the Computer (continued) The Operating System (O/S) l O/S provides fundamental services for all other tasks: odata storage oI/O oProgram execution l O/S is usually stored on disk, but not always: PalmPilot l Once O/S is running, computer can be fully functional.