CMSC 1041 Machine Architecture An Introduction to Computer Components.
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Transcript of CMSC 1041 Machine Architecture An Introduction to Computer Components.
CMSC 104 1
Machine Architecture
An Introduction
to
Computer Components
CMSC 104 2
Major Computer Components
Central Processing Unit (CPU) Bus Main Memory (RAM) Secondary Storage I / O Devices Starting the computer
CMSC 104 3
Computer Functional Diagram
CMSC 104 4
CPU
Central Processing Unit The “brain” Controls all other computer functions
CMSC 104 5
CPU (Continued)
Typeso Intel: 4004, 8008, 8080, 8086, 80186,
80286, 80386, 80486, Pentium, Merced, ?o Motorola: 6800, 6809, 68000, 68020,
68040, 68060, 68080, RISC, ?o DEC: PDP-8/10/11, VAX, Alpha, ARM, ?o AMD: K4, K5, K6, K7, ?o Zilog: Z80, Z800, Z8000 (Still around?)
CMSC 104 6
CPU (Continued)
Just a collection of fast ON/OFF switches
Forty-million transistors in this space (or less)
CMSC 104 7
CPU (Continued)
Some MainFrame CPUs are limited by the speed of light.
CMSC 104 8
The Buss
Different major components are connected by the buss.
A buss is a group of parallel wires (or circuit-board connections) that carry control signals and data between components.
CMSC 104 9
Main Memory
Main memory is made up of two-state devices.
Two state devices have just two possible states (Wow!). An ON/OFF switch is a two-state device.
In memory, one state stands for 1, the other for 0.
CMSC 104 10
Main Memory (Continued)
Memory can hold any type of data that can be represented by a combination of two states --- and only those types.
Examples:1 = yes, 0 = no 01 = Red, 10 = Blue, 11 = Green 00 = 0, 01 = 1, 10 = 2, 11 = 3
CMSC 104 11
Main Memory (Continued)
Memory often made up of capacitors (electron storage devices). “Charged” (“full”) 1, ON, SET. “Discharged” (“empty”)
0, OFF, RESET, CLEARED
CMSC 104 12
Main Memory (Continued)“The Incredible Shrinking Capacitor”
Technology is constantly improvingo Experience smarter engineerso Smarter engineers smaller deviceso Smaller devices cheaper systemso Cheaper systems more saleso More sales more experience
CMSC 104 13
Main Memory (Continued) “The Incredible Shrinking Capacitor”
Memory chips now routinely contain 128x220 (“128 Meg”) bits.
“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 104 14
Main Memory ((still) Continued)
Memory is divided into cells, where each cell contains 8 bits. Remember that 8 bits is called a byte.
Each of these cells are numbered. The number is the cell’s address.
The address is the, um, ah, er, well the “address” we use to specify which byte we want to work with.
CMSC 104 15
Main Memory“Nepenthe: Elixir of Forgetfulness.”
Main memory is volatile (it goes away when you turn off the power).
Capacitors leak charge goes away data is lost.
“If car-makers … and they would disappear as soon as we turned off the engine.”
There are non-volatile memory systems.
CMSC 104 16
Main MemoryReading & Writing (for ‘rithmetic)
In addition to the circuitry that holds the bits, there are other circuits that:o Get the value of the data held at a
particular address --- READ.o Store data at particular address --- WRITE.
o Some memory is designed so that it cannot be written Read-Only Memory ROMo Many types of ROM are non-volatile.
CMSC 104 17
Memory Access
Memory at all addresses can be accessed in the same amount of time.
Memory can be accessed in any order, like cuts on a CD (not “Byte0, Byte1, Byte3, …, ByteN” like cuts on a tape).
Access in any order Random Access Random Access Memory RAM
CMSC 104 18
Secondary Storage
Many Types:o Disks (Random Access)o Tapes (Sequential access)
Persistent storage (Stays when the power goes off)o Programso Data files (binary, text)o System organization (Directory structure)
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I/O
Converts some “real” thing (sound, movement, electrical signal) into bits.
Usually done by specialized “add ons”o Keyboardo Monitoro Soundcard
Sometimes disk and tape drives are considered I/O devices.
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Computer/Peripheral Communication“There be Dragons and Mysteries in these Waters.”
Portso Electronic connections through which data
can enter or leave the computer o Identified by port numbers (like memory
cells are identified by addresses)o Usually each device (keyboard, soundcard,
network card, modem) with be assigned to exclusive use of one or more ports
CMSC 104 21
Computer/Peripheral CommunicationDoesn’t everyone speak Latin ?
I/O devices normally exchange two things with the computer “Data” --- e.g. bits to and from a
modem --- this is what you want “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 104 22
Computer/Peripheral Communication“No thanks, I peel my own.”
Protocol insures that the device and the computer “speak the same language.”Parity (must there be an even number
of bits per exchange?) “Endedness” (some computers
transmit numbers from-left-to-right, others from-right-to-left)
CMSC 104 23
Computer/Peripheral Communication“Let’s not both talk at once”
Usually duplex (two-way) rather than simplex (one-way) Simplex: mail, TV/Radio broadcast.o Half-duplex: two-way communication, but
in communication can occur only in one direction at a time (polite telephone call).
o Full-duplex - allows communication in both directions at the same time.
CMSC 104 24
Computer/Peripheral Communication Controllers
Special-purpose “CPUs” designed to handle I/O
Free main CPU by taking over comms tasks.
Allow more complex I/O, more devices So effective that many machines are
designed to use controllers even if only one device is connected to a port.
CMSC 104 25
Computer/Peripheral Communication Parallel and Serial Communication
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!”
Serial - Transmits one bit at a time. Slower, but uses a simpler data path. “Here’s one bit, here’s another bit …”
CMSC 104 26
Bits, Bytes and Words
A bit is a single 1 or 0; a single choice A byte is 8 bits
o A word is 16 bits or 2 byteso Long word = 4 bytes = 32 bitso Quad word = 8 bytes = 64 bitso Programming languages may use these
terms when organizing data A <what> is 4 bits?? (It’s a small byte.)
CMSC 104 27
More Bits and Bytes
There are 16-, 32-, and 64-bit machines All of UMBC Unix systems are 32-bits
CMSC 104 28
Booting the Computer
It refers to the computers start-up procedure.
Comes from the expression “pulling yourself up by your bootstraps”
Starts with instructions stored in the ROM chips. (Why: two reasons.)
CMSC 104 29
Booting the Computer (continued)
A typical boot sequence:o Test critical components (and maybe all
components).o Turn on and setup critical devices
(console, keyboard, power monitor, operating system storage media)
o Load operating system (usually from disk)o Transfer control to operating system.
CMSC 104 30
Booting the Computer (continued)The Operating System (O/S)
O/S provides fundamental services for all other tasks:o data storageo I/Oo Program execution
O/S is usually stored on disk, but not always: PalmPilot
Once O/S is running, computer can be fully functional.