Chapter 2: Inside the System Unit

1. Chapter 2: Inside the System Unit Lecture # 04 Instructor: Naveedullah Safi

2. The System Unit Next • What is thesystem unit? • Case that contains electronic components of the computer used to process data

3. The System Unit Next • What are common components inside the system unit? • Processor • Memory • Adaptercards • Sound card • Video card • Drive bays • Powersupply

4. The System Unit Next • What is themotherboard? • Main circuit board in system unit • Contains expansion slots, processor chips, and memory slots • Sometimes called a system board

5. Processor Processor Control Unit Arithmetic Logic Unit (ALU) InstructionsDataInformation InstructionsDataInformation Next • What is thecentral processing unit (CPU)? The integrated circuit chip that processes electronic signals is called the central processing unit (CPU). The CPU is also known as a microprocessor or processor. Control Unit Arithmetic Logic Unit (ALU) Memory InputDevices OutputDevices Data Information StorageDevices

6. Processor Memory Processor ALU Control Unit Next • What is amachine cycle? • Four operations of the CPU comprise a machine cycle Step 1. FetchRetrieves the program instruction or data item from memory Step 2. DecodeTranslate instruction into commands Step 4. StoreWrite result to memory Step 3. ExecuteCarry out command

7. Processor • The two main parts of the CPU are the control unit and the arithmetic logic unit. • The control unit retrieves instructions from memory and interprets and performs those instructions. • The control unit manages the machine cycle or processing cycle

8. ALU (Arithmetic Logic Unit) • The arithmetic logic unit (ALU) performs arithmetic and logical operations. • Arithmetic operations involve adding, subtracting, multiplying, and dividing. • Logical operations involve comparisons between two or more data items.

9. Processor • Factors that affect the performance of a CPU include: • The amount of RAM memory. • The speed and generation of your CPU (the system clock) • The size of the Register on your CPU. • The Bus type and speed. • The amount of Cache memory.

10. Processor Next • What is thesystem clock? • Controls timing of all computer operations • The system clock coordinates(Organize) the computer’s internal activities. Pace of system clock is clock speed Most clock speeds are in the gigahertz (GHz) range (1 GHz = one billion ticks of system clock per second)

11. Processor Next • What are dual-core and multi-core processors? • A dual-core processor is a single chip that contains twoseparate processors • A multi-core processor is a chip with two or moreseparate processors • Each processor on a dual-core/multi-core chip generallyruns at a slower clock speed, but increase overall performance

12. Processor • Parallel processing is a method in which more than one processor performs at the same time, resulting in faster processing.

13. Data Representation Next • How do computers represent data? • Most computers aredigital • Recognize only two discrete states: on or off • Use a binary system to recognize two states • Use Number system with two unique digits: 0 and 1, called bits (short for binary digits)

14. Data Representation Next • What is abyte? • Eight bits grouped together as a unit • Provides enough different combinations of 0s and 1s to represent 256 individual characters • Numbers • Uppercase and lowercase letters • Punctuation marks

15. Data Representation Step 1.The user presses the capital letter T (SHIFT+T key) on the keyboard. Step 2.An electronic signal for the capital letter T is sent to the system unit. T Step 4.After processing, the binary code for the capital letter T is converted to an image, and displayed on the output device. Next • How is a letter converted to binary form and back? Step 3.The system unit converts the scan code for the capital letter T to its ASCII binary code (01010100) and stores it in memory for processing.

16. Memory Next • What ismemory? • Electronic components that store instructions, data, and results • Each byte stored in unique location called anaddress, similar to seats in a concert hall

17. Memory Term Abbreviation Approximate Size Kilobyte KB or K 1 thousand bytes Megabyte MB 1 million bytes Gigabyte GB 1 billion bytes Terabyte TB 1 trillion bytes Next • How is memory measured? • By number of bytes available for storage

18. Memory Next • What israndom access memory (RAM)? Memory chips that can be read from and written to by processor Also called main memory Most RAM is volatile, it is lost when computer’s power is turned off The more RAM a computer has, the faster it responds

19. Memory RAM RAM Next • How do program instructions transfer in and out of RAM? Step 1.When you start the computer, certain operating system files are loaded into RAM from the hard disk. The operating system displays the user interface on the screen. Operating system interface Operating system instructions Step 2.When you start a Web browser, the program’s instructions are loaded into RAM from the hard disk. The Web browser window is displayed on the screen. Web browser instructions Web browser window Step 3.When you start a paint program, the program’s instructions are loaded into RAM from the hard disk. The paint program, along with the Web Browser and certain operating system instructions are in RAM. The paint program window is displayed on the screen. Paint program instructions Paint program window Step 4.When you quit a program, such as the Web browser, its program instructions are removed from RAM. The Web browser is no longer displayed on the screen. Web browser program instructions are removed from RAM Web browser window is no longer displayed on desktop

20. Memory Next • How much RAM does a computer require? • Depends on the types of software you plan to use • For optimal performance, you need more than minimum requirements

21. Memory Next • What iscache? • Is a small unit of fast memory built into the processor to improve performance • Is more expensive than RAM • Comes in two types: • Primary cache,found in the microprocessor chip • Secondary cache, located on the circuit board

22. Memory Next • What isread-only memory (ROM)? Memory chips that store permanent data and instructions The data on most ROMchips cannot be modified Firmware—Manufactured with permanently written data, instructions, or information

23. Memory flash memory chips USB port MP3 Player Next • What isflash memory? • Nonvolatile memory that can be erased electronically and rewritten • Used with PDAs, smart phones, printers, digital cameras, automotive devices, audio players, digital voice recorders, and pagers Step 3.Plug the headphones into the portable media player, push a button on the portable media player, and listen to the music through the headphones. Step 1.Purchase and download music tracks from a Web site. With one end of a special cable connected to the system unit, connect the other end to the USB port in the portable media player. Step 2.Instruct the computer to copy the music tracks to the flash memory chip in the portable media player.

24. Memory Term Speed Millisecond One-thousandth of a second Microsecond One-millionth of a second Nanosecond One-billionth of a second Picosecond One-trillionth of a second Next • What isaccess time? • Amount of time it takes processor to read data from memory • Measured in nanoseconds (ns), one billionth of a second • It takes 1/10 of a second to blink your eye; a computer can perform up to 10 million operations in same amount of time

25. Expansion Slots and Adapter Cards Next • What is anexpansion slot? • Socket on the motherboard that can hold an adapter card

26. Ports and Connectors Next • What areportsandconnectors? • Portconnects external devices to system unit • Connector joins cable to peripheral

27. Ports and Connectors Next • What is aserial port? • Transmits one bit of data at a time • Connects slow-speed devices, such as a mouse, keyboard, or modem

28. Ports and Connectors Next • What is aparallel port? • Connects devices that can transfer more than one bit at a time, such as a printer

29. Ports and Connectors Single USB port can be used to attach multiple peripherals using a USB hub The latest version ofUSB is calledUSB 2.0 PCs typically have six to eight USB ports on front or back of the system unit Next • What areUSB ports? USB (universal serial bus) port can connect up to 127 different peripherals together with a single connector

30. Ports and Connectors Next • What areFireWire ports? • Connects multiple types of devices that require faster data transmission speeds • Allows you to connect up to 63 devices together

31. Buses Next • What is abus? • Channel that allows devices inside and attached to the computer to communicate with each other • System bus connects processor and main memory • Data bus width is measured in bits. • The maximum number of bits the CPU can process at once is called the word size. • Word size determines which operating systems and software a CPU can run

32. Power Supply External peripherals might use an AC adapter, which is an external power supply ConvertsAC PowerintoDC Power Next • What is a power supply? AC: Alternating Current DC: Direct Current

33. Mobile Computers and Devices Next • What is amobile computer? • Notebook, weighing between 2.5 and 9 pounds, or mobile device such as a PDA p. 152 Fig. 4-26

34. Mobile Computers and Devices Next • DVI(Digital Visual Interface)

35. Mobile Computers and Devices Next • What ports and slots are on a tablet PC?