1. 0110101001101101 10010110 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

2. 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.

3. 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

4. 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

5. Binary Numbers A digital system
Can represent any decimal number with only two characters: 0 & 1
Why not use decimal numbers? Computers use digital systems (on or off)
Decimal Binary

6. 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 make up computer chips.
AMD Athlon chip has 22 million transistors.
Image courtesy of AMD

7. Binary Code: Bits & Bytes
Bit: a single element of code. 0 or 1.
Contraction of “Binary digit”
Byte: a collection of 8 bits
Possible number of different bytes: etc.

8. 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)

9. When is a kilobyte NOT a kilobyte?
Common usage (not exactly correct, but close)
kilobyte: KB 1,000 bytes megabyte: MB 1,000,000 bytes gigabyte: GB 1,000,000,000 bytes terabyte: TB 1,000,000,000,000 bytes

10. 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

11. 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

12. The CPU CPU terms CPU brands & models capacity, -bit clock speed, MHz
CISC, RISC
CPU brands & models
image courtesy of AMD.com

13. 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

14. 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

15. 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.)

16. 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

17. ! 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.

18. 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

19. Types of chips: AMD AMD Athlon XP - specs AMD Athlon - specs
Designed for Windows XP, (works w/ other OS’s)
Up to 1.67 GHz (but runs faster than Pentium GHz)
integrated 256 KB L2 cache
266 MHz system bus
AMD Athlon - specs
up to 1.4 GHz
AMD Duron – specs
economical
up to 1.3 GHz
128 KB L1 cache, 64 KB L2 cache
images courtesy of AMD

20. Types of Chips: Other Brands
Cyrix MII
Motorola PowerPC
Apple
Sun
Digital
others available
images courtesy of Sun