1. Chapter 2: The System Unit

2. Computing Fundamentals Chapter 2: The System Unit Learning Objectives: Recognize how data is processed Understand processors Understand memory types and functions Identify and use ports and buses Troubleshoot common system unit problems 2

3. Computing Fundamentals Understanding CPUs Every computer has at least one processor, also called Central Processing Unit (CPU) The CPU contains millions of tiny transistors and pathways that: take in data and instructions, process (calculate) the data according to the instruction, and output the results of the calculations 3

4. Computing Fundamentals Understanding CPUs Every CPU includes the following components: Control Unit Manages the flow of data through the CPU Arithmetic Logic Unit (ALU) Does the actual processing Receives data and instructions and delivers a result Registers Holding areas for data and instructions Different registers, each with its own special purpose (e.g. for holding data, for holding instructions, for storing logical states (yes/no) etc.) 4

5. Computing Fundamentals Physical Composition of a CPU A very thin sheet of semiconductor material (silicon) with a complex array of tiny transistors and buses Semiconductor material does not affect the electrical flow (electricity-neutral) Encased in a ceramic shell for its protection and mounted on a small circuit board The underside of the CPU contains tiny pins or contacts (metal dots) Each pin or dot is a separate communication line, carrying a different piece of data 5

6. Computing Fundamentals Physical Composition of a CPU 6 Most modern PC CPUs have multiple cores Completion of multiple tasks simultaneously Common numbers of cores are 2, 4, or 6 e.g. most models of Intel i7 processor have four cores Core A set of the essential processor components that work together (control unit, ALU, and registers) All located on the same chip of the CPU Multiple cores allows parallel processing for greater throughput

7. Computing Fundamentals Clock Cycle The CPU is capable of executing a function with every tick of the system clock the system clock (called a clock cycle). However, in practice, the CPU sometimes is idle because there is a delay between the request for data to be retrieved from memory and its delivery. A delay caused by waiting for another component to deliver data is called latency. 7

8. Computing Fundamentals Cache To help minimize latency, CPUs have caches. A cache is a small amount of very fast memory located near (or within) the CPU. Data that the CPU has recently used, or is predicted to need soon, is placed in the cache for temporary holding. That way, if the CPU calls for the data, it’s more readily available and there is less delay. 8

9. Computing Fundamentals CPU Performance Factors The most obvious performance factor for a CPU is its maximum speed, measured in billions of hertz, or gigahertz (GHz). Hertz: One cycle per second, a measurement of activity speed. A CPU’s word size also makes a difference. Word Size is the number of bits that the CPU can accept as input simultaneously, either 32bit or 64bit. 9

10. Computing Fundamentals CPU Performance Factors Because modern CPUs have many technology improvements in them, speed and word size alone do not form a reliable benchmark of a CPU’s capability. Benchmark A consistent measurement of performance. Another way to look at performance is how many instructions per second the CPU can process. Instructions per second: A measurement of a CPU’s throughput capability, taking into consideration factors such as number of cores and latency. 10

11. Computing Fundamentals Understanding Memory Static (non-volatile): Memory that retains its data without electricity being constantly applied. Dynamic (volatile): Memory that must be constantly refreshed. It stores data until the computer is turned off 11

12. Computing Fundamentals Understanding Memory Random Access Memory (RAM): that can have its values changed freely, an unlimited number of times. Read-Only Memory (ROM) In general, memory that cannot be rewritten. However, there are exceptions to that in newer types of ROM. Electrically Erasable Programmable ROM (EEPROM): ROM that can be erased and reprogrammed with electricity. 12 In other words:  RAM = rewriteable  ROM = not rewriteable (with exceptions)

13. Computing Fundamentals How Computers Use Memory Computers use different types of memory in various ways: 1.System memory (main memory) Such as the RAM installed in PC’s motherboard. Systems Memory is dynamic RAM (DRAM). 13

14. Computing Fundamentals Understanding System Memory Each computer has a certain amount of system memory: called also RAM or main memory Is a dynamic RAM (DRAM) Loses content if not constantly electrically refreshed The more memory, the more applications and file that can be opened at once. Virtual memory is simulated memory by data- swapping on/off the hard drive Used as extension to main memory Paging file (called also swap file) is the area of the hard drive dedicated for virtual memory 14

15. Computing Fundamentals How Computers Use Memory 2.Component memory (printers, display adapters): Many components have a small amount of memory built in for their own use. Example: A printer might have RAM (typically DRAM) that holds information on page being printed. 15

16. Computing Fundamentals How Computers Use Memory 3.ROM-BIOS (EEPROM chip): contains low-level startup instruction for the hardware. use a type of EEPROM to store data. Not rewritable except with a special utility program. 4.CPU caches: a type of static RAM. 5.USB flash drives, Memory cards, Solid-state hard drives: use a type of EEPROM to store data, called flash memory Data can be written and rewritten multiple times 16

17. Computing Fundamentals Memory’s Physical Form System memory comes mounted on small rectangular circuit, called Dual inline memory modules (DIMMs). Circuit boards fit into memory slots on motherboard Different types and speeds of DIMMs. Capacity ranges from 2, 4 or 8 GB of RAM. Small-outline DIMMs (SO-DIMMs) for portables such notebooks. 17 Some DIMMs have a metal plate covering the chips for better heat dissipation.

18. Computing Fundamentals Memory’s Physical Form Most common type of DRAM is known as SDRAM. Synchronous DRAM (SDRAM) synchronizes with the system bus speed (operates at the speed of the system clock). Two types Single data rate SDRAM (SDR SDRAM) Performs one action per clock tick. Double data rate (DDR SDRAM) Performs two action per clock tick 18

19. Computing Fundamentals Understanding Motherboards Motherboard: large circuit board inside the computer Capabilities dictated by chipset. Chipset: The controller chip on a circuit board. Form factor: size and shape of motherboard. 19

20. Computing Fundamentals Understanding Motherboards Expansion Slot: A slot in the motherboard into which an expansion card (a small circuit board) can be installed. Expansion Card A small circuit board that fits into a slot on the motherboard to add functionality. 20 Expansion slotsExpansion card

21. Computing Fundamentals Understanding Motherboards PCI (Peripheral Component Interface): A motherboard slot that accepts PCI expansion boards. PCI is considered a legacy interface (mostly obsolete) PCI Express (PCIe): A new and updated version of the PCI motherboard slot. 21

22. Computing Fundamentals Understanding Motherboards ExpressCard slot in notebooks adds a capability to the system, such as wireless networking PCI Express Mini Card socket in notebooks small circuit board that can be installed in a notebook PC’s PCI Express Mini expansion bay to add a new capability 22

23. Computing Fundamentals Built-In Components Graphics Ports: Digital Visual Interface (DVI): A digital port for connecting a monitor to a PC. Video Graphics Array (VGA): An analog port for connecting a monitor to a PC. 23

24. Computing Fundamentals Built-In Components Speakers/Headphones 3.5 mm Ethernet networking RJ-45 jack Resembles a wide telephone plug Universal Serial Bus (USB) general-purpose port for connecting external devices to a PC. USB 1.1, 2.0, 3.0 speeds FireWire (IEEE 1394) for high-speed connection, such as some external hard drives and video cameras. 24

25. Computing Fundamentals Different USB Types * 25 USB 3.1 Type C First Reversible USB Port

26. Computing Fundamentals Built-In Components (Legacy) PS/2 Used for older keyboards and mice Parallel Port Used for older printers Serial Port Used only for very old components (mice, modems) 26

27. Computing Fundamentals Drive Connectors Parallel ATA (PATA) Older hard disk drives Older CD and DVD drives Serial ATA (SATA) Newer hard disk drives Newer CD and DVD drives Solid-state hard drives 27

28. Computing Fundamentals Understanding Power Supplies Power supply has two functions: Converts AC (Alternating Current) to DC direct current. Decreases the voltage to the appropriate levels for the devices it powers 28

29. Computing Fundamentals Understanding Power Supplies 29 A power connector for a Serial ATA (SATA) hard drive.. Fig. This connector runs from the power supply to the motherboard, delivering all the different voltages that devices that connect directly into the motherboard might need.

30. Computing Fundamentals Notebook Power Supply Transformer block (brick): A thick block built into a power cable for a device that handles the conversion of AC power to DC and decreases the voltage to the level needed. 30

31. Computing Fundamentals Key Terms 31 active heat sink benchmark cache Central Processing Unit (CPU) chipset CMOS setup core Digital Visual Interface (DVI) double data rate (DDR) dual inline memory module (DIMM) dynamic memory Electrically Erasable Programmable ROM (EEPROM) expansion cards expansion slots ExpressCard form factor gigahertz (GHz) hard reset heat sink hertz IEEE 1394A instructions per second latency machine cycle memory address motherboard overclock paging file Parallel ATA parallel port PCI Express (PCIe) PCI Express Mini Card Peripheral Component Interface (PCI) POST card power supply power-on self test (POST) PS/2 Random Access Memory (RAM) Read-Only Memory (ROM) RJ-45 jack semiconductor Serial ATA serial port single data rate (SDR) soft reset static memory swap file synchronous dynamic RAM (SDRAM) system clock system memory transformer block Universal Serial Bus (USB) Video Graphics Adapter (VGA) virtual memory word size

32. Computing Fundamentals Summary 1. What are the three basic components inside a CPU? 2. What are the four steps of the machine cycle, and how do the parts you named in #1 fit into it? 3. How do the L1, L2, and L3 caches improve CPU performance? 4. What is the difference between static and dynamic memory? 5. What are four ways in which one motherboard may differ from another? 6. Why does a power supply have different colored wires? 32