1. The System Unit: Processing and Memory
Lecture 2
The System Unit:
Processing and Memory
Inside the Computer: 1

2. Quick Quiz
1. A tablet PC is an example of a(n) _____________. a. Desktop computer b. Portable PC c. Internet appliance 2. True or False: A smartphone is an example of a mobile device

3. Data vs. Information Data Raw, unorganized facts
Can be in the form of text, graphics, audio, or video
Information
Data that has been processed into a meaningful form
Information processing
Converting data into information

4. Data and Program Representation
In order to be understood by a computer, data and programs need to be represented appropriately
Coding systems: Used to represent data and programs in a manner understood by the computer
Digital computers: Can only understand two states, off and on (0 and 1)
Digital data representation: The process of representing data in digital form so it can be understood by a computer

5. Digital Data Representation
Bit: The smallest unit of data that a binary computer can recognize (a single 1 or 0)
Byte = 8 bits
Byte terminology used to express the size of documents and other files, programs, etc.
Prefixes are often used to express larger quantities of bytes: kilobyte (KB), megabyte (MB), gigabyte (GB), terabyte (TB), petabyte (PB), exabyte (EB), zettabyte (ZB), yottabyte (YB).
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6. Data and Program Representation Representing Numerical Data
Representing Numerical Data: The Binary Numbering System
Numbering system
A way of representing numbers
Decimal numbering system
Uses 10 symbols (0-9)
Binary numbering system
Uses only two symbols (1 and 0) to represent all possible numbers
In both systems, the position of the digits determines the power to which the base number (such as 10 or 2) is raised

7. Data and Program Representation Representing Numerical Data

8. Data and Program Representation Coding Systems for Text-Based Data
ASCII (American Standard Code for Information Interchange):
coding system traditionally used with personal computers

9. Data and Program Representation Coding Systems for Text-Based Data
Unicode: newer code (32 bits per character is common); universal coding standard designed to represent text-based data written in any ancient or modern language
Replacing ASCII as the primary text-coding system

10. Data and Program Representation
Graphics (still images such as photos or drawings)
Bitmapped images: A variety of bit depths are possible (4, 8, 24 bits)
More bits = more colors

11. Data and Program Representation
Audio data: Must be in digital form in order to be stored on or processed by a computer
Often compressed when sent over the Internet
MP3 files
Video data: Displayed using a collection of frames, each frame contains a still image
Amount of data can be substantial, but can be compressed
Developers keep on defining new formats aiming for more quality with less space.

12. Data and Program Representation Representing Programs: Machine Language
Machine language: Binary-based language for representing computer programs the computer can execute directly
Early programs were written in machine language.
Today’s programs still need to be translated into machine language in order to be understood by the computer
Most programs are written in other programming languages
Language translators are used to translate the programs into machine language

13. Quick Quiz 1. Another way to say “one million bytes” is
a. one kilobyte
one gigabyte
one megabyte
2. True or False: MP3 files are stored using 0s and 1s.  
3. The _____________ numbering system is used by computers to perform mathematical computations.
Answers:
1) c; 2) True; 3) binary

14. Computer System
All the elements in a stereo system have their counterparts in a computer system. At a minimum, a computer system consists of the computer itself and its peripheral equipment. Also often included are the machine-readable instructions and facts it processes, as well as operating manuals, procedures, and the people who use the system. In other words, all the components that contribute to making the computer a useful tool can be said to be part of a computer system.
At the heart of any computer system—equivalent to the stereo amplifier—is the computer itself, or central processing unit (CPU). Like a stereo amplifier, the computer can't do anything useful without support equipment for input and output, and I/O media for storage.
A computer has a memory that allows it to store whatever input it receives and whatever results it produces from these inputs. A stereo amplifier has no memory—what's playing on the CD player or tape recorder passes directly through the amplifier to the speakers. Because a computer can store materials in its memory, it can be directed to rearrange or recombine those materials in an amazing variety of ways before it sends them along as output.

15. Hardware Input devices Used to input data into the computer
Keyboards, mice, scanners, cameras, microphones, joysticks, touch pads, touch screens, fingerprint readers, etc.
Processing devices
Perform calculations and control computer’s operation
Central processing unit (CPU) and memory
Output devices
Present results to the user
Monitors, printers, speakers, projectors, etc.

16. Hardware Storage devices
Used to store data on or access data from storage media
Hard drives, CD/DVD discs and drives, USB flash drives, etc.
Communications devices
Allow users to communicate with others and to electronically access remote information
Modems, network adapters, etc.

17. Inside the System Unit
The system unit of a PC is the case that houses processing hardware and other hardware.
All of the hardware contained within the system unit is connected to the system board or motherboard.

18. Multicore

19. System board (Motherboard)

20. The CPU
Central processing unit (CPU): circuitry and components packaged together and connected directly to the motherboard
Does the vast majority of processing for a computer
Also called a processor; called a microprocessor when talking about personal computesr
Dual-core CPU: Contains the processing components (cores) of two separate processors on a single CPU
Quad-core CPU: Contains 4 cores
Typically different CPUs for desktop computers, portable computers, servers, mobile devices, consumer devices, etc.
Often made by Intel or AMD

21. The CPU

22. Intel Processors Table 6-1 Current Intel processors
A+ Guide to Managing and Maintaining Your PC, 7e

23. AMD Processors Table 6-2 Current AMD processors
A+ Guide to Managing and Maintaining Your PC, 7e

24. The CPU

25. Processing Speed CPU clock speed: One measurement of processing speed
Measured in megahertz (MHz) or gigahertz (GHz)
Higher CPU clock speed = more instructions processed per second
Other factors (CPU architecture, memory, bus speed, amount of RAM, etc.) also affect the overall processing speed of a computer
Benchmark tests: Can be used to evaluate overall processing speed

26. Word Size and Cache Memory
Word size: The amount of data that a CPU can manipulate at one time
Typically 32 or 64 bits
Cache memory: Special group of very fast memory chips located on or close to the CPU
Level 1 is fastest, then Level 2, then Level 3
More cache memory typically means faster processing
Usually internal cache (built into the CPU)
Often some cache dedicated to each core; may also have some shared cache accessible by any core

27. Bus Width, Bus Speed, and Bandwidth
Bus: An electronic path over which data can travel
Bus width: The number of wires in the bus over which data can travel
Bus width and speed determine the throughput (or bandwidth) of the bus
The amount of data that can be transferred by the bus in a given time period

28. PC Buses and Ports ISA Slow-speed devices like mouse, modem PCI
High-speed devices like hard disks and network cards
AGP
Connects memory and graphics card for faster video performance
USB
Supports “daisy-chaining” eliminating the need for multiple expansion cards; hot-swappable
IEEE 1394 (FireWire)
High-speed bus connecting video equipment to the computer
PC Card
Credit card sized PC card devices normally found on laptops

30. PC Cards

32. Memory Memory refers to chip based storage
RAM (random access memory): Computer’s main memory
Consists of chips arrange on a circuit board called a memory module plugged into the motherboard
Stores essential parts of operating system, programs, and data the computer is currently using
Adequate RAM is needed to run programs
Volatile: Contents of RAM is lost when the computer is shut off
Most personal computers use SD-RAM (Synchronous dynamic random-access memory)
MRAM and PRAM: non-volatile RAM under development

33. Memory
Registers: High-speed memory built into the CPU; used by the CPU
ROM (read-only memory): Non-volatile chips located on the motherboard into which data or programs have been permanently stored
Retrieved by the computer when needed
Being replaced with flash memory for firmware
Flash memory: Type of nonvolatile memory that can be erased and reprogrammed
Some flash memory chips are used by the computer
Flash memory chips are also used in flash memory storage media (sticks, cards, and drives)

34. RAM & ROM Random Access Memory Read Only Memory main memory
Volatile meaning it is lost when power is turned off
SIMMs - groups of RAM ready to plug into the system board
DRAM - ordinary RAM
SRAM - faster type of RAM
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Read Only Memory
Non-volatile meaning contents are not lost when power is shut off
Contents are Read Only
Faster than disk for storing critical files or data
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RAM
RAM, for random access memory, is used to store the programs and data on which the computer is currently working.
RAM is volatile, meaning that the contents of memory are lost when the computer is shut off.
Every time the CPU requests data from RAM, it places a copy of them in cache memory. When the CPU needs data from RAM, it checks first to see if cache holds needed input; if so, it can retrieve the data more quickly from cache than from RAM.
ROM
ROM, which stands for read-only memory, consists of nonerasable hardware modules that contain programs.
Key pieces of systems software are often stored in ROM.

35. Quick Quiz
1. Which type of memory is erased when the power goes out? a. ROM b. RAM c. flash memory 2. True or False: The CPU can also be called the motherboard. 3. A(n) electronic path within a computer over which data travels is called a(n) _____________. Answers: 1) b; 2) False; 3) bus

36. How the CPU Works
CPU: Consists of a variety of circuitry and components packaged together
Transistor: Key element of the microprocessor
Made of semi-conductor material that acts like a switch controlling the flow of electrons inside a chip
Today’s CPUs contain hundreds of millions of transistors; the number doubles about every 18 months (Moore’s Law)
Transistor

37. How the CPU Works Typical CPU Components Arithmetic/Logic Unit (ALU)
Performs arithmetic involving integers and logical operations
Floating Point Unit (FPU)
Performs decimal arithmetic
Control Unit
Coordinates and controls activities within a CPU core
Prefetch Unit
Attempts to retrieve data and instructions before they are needed for processing in order to avoid delays

38. The Little Man Computer

39. How the CPU Works Decode Unit
Translates instructions from the Pre-fetch unit so they are understood by the control unit, ALU, and FPU
Registers and Internal Cache Memory
Store data and instructions needed by the CPU
Bus Interface Unit
Allows the core to communicate with other CPU components

40. Courtesy: Course Technology/Cengage Learning
Figure 6-2 Since the Pentium processor was first released in 1993, the standard has been for a processor to have two arithmetic logic units so that it can process two instructions at once
Courtesy: Course Technology/Cengage Learning
A+ Guide to Managing and Maintaining Your PC, 7e

41. Typical CPU Components

42. How the CPU Works The System Clock and the Machine Cycle
System clock: Timing mechanism within the computer system that synchronizes the computer’s operations
Each signal is a cycle
Number of cycles per second = hertz (Hz)
Many PC system clocks run at 200 MHz
Computers can run at a multiple or fraction of the system clock
For instance, with a CPU clock speed of 2 GHz, the CPU clock “ticks” 10 times during each system clock tick
During each CPU clock tick, one or more pieces of microcode are processed

43. The System Clock and the Machine Cycle
Machine cycle: The series of operations involved in the execution of a single machine level instruction
Fetch: The program instruction is fetched
Decode: The instructions are decoded so the control unit, ALU, and FPU (Floating-Point Unit )can understand them
Execute: The instructions are carried out
Store: The original data or the result from the ALU or FPU execution is stored in the CPU’s registers

44. How a Processor Works (cont’d.)
Three methods to improve performance
Multiprocessing
Processor contains more than one ALU
Multiple processors
Installing more than one processor on a motherboard
Multi-core processing
Processor housing contains two or more cores operating at same frequency, independently of each other
Dual core, triple core, quad core, octo core
A+ Guide to Managing and Maintaining Your PC, 7e

45. Which of the following statements is true?
(a) Hardware controls software
(b) Software commands the computer to perform actions and make decisions
(c) C is an object oriented programming language
(d) Both (b) and (c)

46. The smallest data item in a computer, called a ________, can assume the value 0 or the value 1.
(a) bit
(b) character
(c) field
(d) digit
The process of representing data in digital form so it can be used by a digital computer is called decimal byte representation.
True b. False

47. Unlike ASCII, Unicode is a universal coding standard designed to represent text-based data written in any language, including those with different alphabets.
True b. False
The number of bits being transmitted at one time is dependent on the bus width.
True b. False

48. ROM (read-only memory), also called main memory, is used to store the essential parts of the operating system while the computer is running.
True b. False
The ____ takes instructions from the prefetch unit and translates them into a form that the control unit can understand
Register ALU
decode internal cache