17 binary code & cpus digital signals

9/17 Binary Code & CPUs

• Digital Signals– digital versus analog, examples

• Binary Numbers– Transistors: introduction

• Binary Code– bits & bytes– types: ASCII, UNICODE, EBCDIC

• CPUs– Parts of a sample CPU– Types of CPUs available

011010100110110110010110

Digital Signals: why they are discussed.

• Virtually everything in a computer runs in a digital system: data storage, communication, output on the screen, …

• Everything is in its lowest form either ON or OFF, UP or DOWN, YES or NO.

• Bits & bytes are combinations of digital signals and codes.

Digital Signals: what are they?

• Digital signals have two settings: ON or OFF.• Examples: smoke signals, Morse code,

fluorescent lights, pass or fail• Anything that can be compared to ON or OFF can

be a digital signal:– Magnets: north or south– Voltage: high or low– Light: light or dark– Gates: open or shut

Digital Signals versus Analog Signals

• Digital signals have two settings: ON or OFF.

• Analog signals have ranges of settings: dimmer switches, human voices, ocean waves

• Sound: Digital versus analog.– Analog is a wave: continuous, gradual– Digital is a step: non-continuous, ON/OFF

Analog signal Digital signal

Binary Numbers

• A digital system• Can represent any decimal

number with only two characters: 0 & 1

• Why not use decimal numbers? Computersuse digital systems (on or off)

Decimal Binary 0 0 1 1 2 10 3 11 4 100 5 101 6 110 7 111 8 1000 9 100110 101011 101112 1100

Transistors: tiny ON/OFF switches• Tiny electrical gates with two paths:

1. Control path (gatekeeper) 2. Signal path (goes through gate)

• Only two possible states: gate is OPEN or gate is CLOSED.

• Transistors are what makeup computer chips.– AMD Athlon chip has 22

million transistors.

Image courtesy of AMD

Binary Code: Bits & Bytes• Bit: a single element of code. 0 or 1.

– Contraction of “Binary digit”• Byte: a collection of 8 bits. 00000000.

– Possible number of different bytes: 25600000000 00000001 00000010 00000011 0000010000000101 00000110 00000111 00001000 0000100100001010 00001011 00001100 00001101 0000111000001111 00010000 00010001 00010010 0001001100010100 00010101 00010110 00010111 0001100000011001 00011010 00011011 00011100 0001110100011110 00011111 etc.

Binary Code: Bits & Bytes• Each byte represents 1 character or command.• A simple text file ( log.txt ) can be only a few

hundred bytes. A spreadsheet ( book1.xls ) can be millions.

• kilobyte: KB 2 to the 10th (1,024) bytes.megabyte: MB 2 to the 20th (1,048,576) gigabyte: GB 2 to the 30th (1,073,741,824)terabyte: TB 2 to the 40th (1,099,511,627,766)

When is a kilobyte NOT a kilobyte?• Common usage (not exactly correct, but close)• kilobyte: KB 1,000 bytes

megabyte: MB 1,000,000 bytesgigabyte: GB 1,000,000,000 bytes terabyte: TB 1,000,000,000,000 bytes

Why we don’t type in binary digits.• Codes (lookup tables) in the computer.• Each character corresponds to a byte.• As we type, the keystrokes are translated into

bytes by the computer.• The computer reverse-translates to show the

characters on the monitor.• Common code sets: ASCII, UNICODE, EBCDIC

Code Types.• ASCII “As-key” American Standard Code for

Information Interchange.– 1st half of the slots in the table are for “standard”

ASCII characters. The second half contains the “extended” ASCII character set.

• UNICODE uses 2 bytes/char rather than 1. – Supports many more characters (34,168). Esp. used

for non-English languages• EBCDIC “eb-see-dik” Extended Binary Coded

Decimal Interchange Code.– Mainly used on mainframe computers

The CPU• CPU terms

– capacity, -bit– clock speed, MHz – CISC, RISC

• CPU brands & models

image courtesy of AMD.com

CPU: Central Processing Unit• The Microprocessor or

CPU (Central Processing Unit) is the “brains” of the computer.

• All other components (RAM, monitor, disk drive) act like bridges to link you & the processor.

image courtesy of AMD.com

Coprocessors• Coprocessors are also

in PC’s. • They handle functions

like graphics, 3-D acceleration, and sound cards.

• Help reduce the load on the main processor.

image courtesy of How Computers Work

Data Capacity• refers to the amount of data that the processor can

process at one time. If a number is bigger than what the processor can handle, it breaks it down into manageable parts, processes it, and puts it back together.

• 8 bit processor: handles numbers up to 8 bits long (2 to the 8th power: 256)

• 16 bit processors handle numbers up to 2 to the 16th power or 65,536)

• 32, 64 bit processing (etc.)

Clock Speed• Timer that everything in the processor uses as a

pacesetter.• Measured in MegaHertz (millions of cycles per

second)• Same model of processors can have their

clock speeds compared. • Different models of processors

cannot be compared so easily.

image from http://web.scps.k12.fl.us/site/agenda/default.htm

Instruction Sets• A chip’s vocabulary.• Types of instructions that a chip can perform.• Bigger does not necessarily equal better in

instruction sets.• CISC: Complex instruction set chips

– use complex instructions to process instructions.• RISC: Reduced instruction set chips

– break down instructions before processing with a simpler instruction set.

!

Types of chips: Intel• Intel Pentium 4 – specs

– Up to 2.20 GHz– Rapid execution engine

• Intel Pentium III - specs– up to 1.33 GHz– 70 new instructions for 3D, voice recognition, etc.– integrated 256 KB L2 cache

• Intel Celeron - specs– economy chip– up to 1.30 MHz– integrated 128 KB L2 cache

images courtesy of TigerDirect.com, Intel

Types of chips: AMD• AMD Athlon XP - specs

– Designed for Windows XP, (works w/ other OS’s)– Up to 1.67 GHz (but runs faster than Pentium 4 2.0 GHz)– integrated 256 KB L2 cache– 266 MHz system bus

• AMD Athlon - specs– up to 1.4 GHz – integrated 256 KB L2 cache– 266 MHz system bus

• AMD Duron – specs– economical– up to 1.3 GHz– 128 KB L1 cache, 64 KB L2 cache images courtesy of AMD

Types of Chips: Other Brands• Cyrix MII• Motorola PowerPC• Apple• Sun• Digital• others available

images courtesy of Sun