Chapter 5 The System Unit

Chapter 5 -The System Unit The system unit also known as the system chassis: is a container that houses most of the electronic components that make up a computer system The five most common types of personal computer : desktop, laptop, tablet, smartphones, and wearable computers. Each has a unique type of system unit. 1- Desktops (the most powerful type ) Most desktops have their system unit in a separate case. Desktop system units that are placed vertically are sometimes referred to as a tower unit or tower computer. So e desktop o pute s, like Apple’s iMa , ha e thei o ito a d s ste the same case. These computers are known as an all-in-one. u it housed togethe i 2- Laptops are portable and much smaller than desktops . Their system units are housed with selected secondary storage devices and input devices. There are several specialized laptops with features that make them unique. Some of them are: • Two-in-one laptops, which include a touch screen and the ability to fold flat like a tablet computer. These laptops offer the advantages of a laptop with the convenience of a tablet. • Gaming laptops, which include high-end graphics hardware and very fast processors.gaming laptops have become the favorite primarily due to the gamers portability. • Ultrabooks, also known as ultraportables or mini notebooks, which are lighter and thinner with longer battery life than most laptops. They accomplish these advantages by leaving out components such as optical drives and using energy-efficient microprocessors. 3- Tablets, They are effectively a thin slab that is almost all monitor with the system unit located behind the monitor. Tablets are smaller, lighter, and generally less powerful than laptop computers. Like a laptop, tablets have a flat screen but typically do not have a standard keyboard. Instead, most tablets use a virtual keyboard that appears on the screen and is touch-sensitive. Inputting information can be diffcult using virtual keyboard,so there is ways to overcome the limitation : • Keyboard attachments. For example, Apple and Logitech offer wireless keyboards for tablets. • Digital pens. These devices assist in selecting options and entering handwritten notes. For example, both Microsoft and Samsung offer tablets with digital pens. • Speech recognition. This advance allows direct verbal communication. 26 Mini tablets are a type of tablet with a smaller screen. While mini tablets operate like a traditional tablet, they typically do not have all the functionality of the bigger tablets. Their most significant advantage is that they are easier to transport in pockets and purses. 4- Smartphones: the most popular mobile device, have become the indispensable handheld computer. In addition to capturing and sending audio and video, smartphones run apps, connect to the Internet, and more.  Their system unit is located behind the display screen. 5- Wearable Computers ( wearable devices), are one of the first evolutionary steps to the IoT. These devices contain an embedded computer on a chip that is typically much smaller and less powerful tha a s a tpho e’s. The ost o o ea a le o pute s a e s a t at hes a d a ti it trackers. • S a t at hes like Apple’s Wat h. This de i e a ts as a at h, fit ess onitor, and communication device. • A ti it t a ke s like Fit it’s Fle . This de i e o ito s dail e e ise a d sleep patte s. It also connects wirelessly to desktops, laptops, and smartphones to record and share data. Components all personal computers share surprisingly similar components, including system boards, microprocessors, and memory. System Board( the mainboard or motherboard) The system board controls communications for the entire computer system. All devices and components connect to the system board, including external devices and internal components.  The system board acts as a data path and traffic monitor, allowing the various components to communicate efficiently with one another. It is a large flat circuit board covered with a variety of different electronic components including sockets, slots, and bus lines. • Sockets provide a connection point for small specialized electronic parts called chips.  Chips consist of tiny circuit boards etched onto squares of sandlike material called silicon. These circuit boards can be smaller than the tip of your finger  A chip is also called a silicon chip, semiconductor, or integrated circuit.  Chips typically are mounted onto chip carriers. These carriers plug either directly into sockets on the system board or onto cards that are then plugged into slots on the system board. Sockets are used to connect the system board to a variety of different types of chips, including microprocessor and memory chips. • Slots provide a connection point for specialized cards or circuit boards. These cards provide expansion capability for a computer system. For example, a wireless networking card plugs into a slot on the system board to provide a connection to a local area network. • Bus lines provide pathways that support communication among the various electronic components. 27 Microprocessor The central processing unit (CPU) or processor is contained on a single chip called the microprocessor. The i op o esso is the ai s of the o pute s ste . It has two basic components:. 1- Control unit: The control unit tells the rest of the computer system how to carry out a p og a ’s i st u tio s. 2- Arithmetic-logic unit: The arithmetic-logic unit (ALU), performs two types of operations: arithmetic and logical. (a) Arithmetic operations are the fundamental math operations: addition, subtraction, multiplication, and division. (b) Logical operations consist of comparisons such as whether one item is equal to (=), less than () the other. Microprocessor Chips Chip processing capacities are often expressed in word sizes. A word is the number of bits (such as 16, 32, or 64) that can be accessed at one time by the CPU.  The more bits in a word, the more data a computer can process at one time.  (( Byte= 8 bits ))A 32-bit-word computer can access 4 bytes at a time. A 64-bit-word computer can access 8 bytes at a time. Therefore, the computer designed to process 64-bit words has greater processing capacity. Othe fa to s affe t a o pute ’s p o essi g apa ilit i ludi g ho fast it a process data and instructions.  The processing speed of a microprocessor is typically represented by its clock speed,( which is related to the number of times the CPU can fetch and process data or instructions in a second.)  Logically, the higher a microprocessor’s lo k speed, the faste the i op o esso . Many personal computers have multicore processors that can provide two or more separate and independent CPUs.  For multicore processors to be used effectively, computers must understand how to divide tasks into parts that can be distributed across each core—an operation called parallel processing.  Operating systems such as Windows 8 and Mac OS X support parallel processing. Specialty Processors A variety of more specialized processing chips have been developed: • Coprocessors designed to improve specific computing operations. the most widely used is the graphics coprocessor, called GPU (graphics processing unit). • Ma a s ha e o e tha 7 sepa ate spe ialt p o esso s to o t ol ea l e e thi g f o efficiency to satellite entertainment and tracking systems. fuel 28 Memory Memory is a holding area for data, instructions, and information. Memory is contained on chips connected to the system board. There are three wellknown types of memory chips: I. RAM Random-access memory (RAM) chips hold the program (sequence of instructions) and data that the CPU is presently processing.  RAM is called temporary or volatile storage because everything in most types of RAM is lost as soon as the computer is turned off. It is also lost if there is a power failure or other disruption of the electric current going to the computer.  Secondary storage, does not lose its contents. It is permanent or nonvolatile storage, such as the data stored on a hard disk. Cache memory improves processing by acting as a temporary high-speed holding area between the memory and the CPU. How the cache works : The computer detects which information in RAM is most frequently used and then copies that information into the cache. When needed, the CPU can quickly access the information from the cache  additional RAM can be added to a computer system by inserting an expansion module called a DIMM (dual in-line memory module) into the system board.  The capacity or amount of RAM is expressed in bytes. Even if your computer does not have enough RAM to hold a program, it might be able to run the program using virtual memory.  With virtual memory, large programs are divided into parts and the parts are stored on a secondary device, usually a hard disk. Each part is then read into RAM only when needed. In this way, computer systems are able to run very large programs II. ROM Read-only memory (ROM) chips have information stored in them by the manufacturer.  Unlike RAM chips, ROM chips are not volatile and cannot be changed by the user.  Read o l ea s that the CPU a ead, o et ie e, data a d programs written on the ROM hip , ut a ’t write—encode or change—the information or instructions in ROM. III. Flash Memory Flash memory offers a combination of the features of RAM and ROM: Like RAM, it can be updated to store new information. Like ROM, it does not lose that information when power to the computer system is turned off . It is used to store the start-up instructions for a computer (This information is called the syste ’s BIOS asi i put/output s ste ). 29 Expansion Slots and Cards Users can insert optional devices known as expansion cards into the slots.  Ports on the cards allow cables to be connected from the expansion cards to devices outside the system unit. Some of the most commonly used expansion cards are: • Graphi s ards, which provide high-quality 3D graphics and animation for games and simulations. This card can contain one or more GPU chips and is standard for most gaming computers. • Net ork i terfa e ards NIC , also known as network adapter cards, which are used to connect a computer to a network. • Wireless et ork ards allow computers to be connected without cables. Example of expansion cards : SD cards . Bus Lines A bus line—also known as a bus—connects the parts of the CPU to each other. also link the CPU to various other components on the system board. A bus is a pathway for bits representing data and instructions. bus width: The number of bits that can travel simultaneously down a bus .The number of traffic lanes determines the bus width. Every computer system has two basic categories of buses. 1. system buses, connects the CPU to memory on the system board. 2. expansion buses, connects the CPU to other components on the system board, including expansion slots. different types of expansion buses : A. Universal serial bus (USB) External USB devices are connected from one to another or to a common point or hub and then onto the USB bus. The USB bus then connects to the PCI bus on the system board. The current USB standard is USB 3.1. B. FireWire buses :connects audio and video equipment to the system board. C. PCI Express (PCIe) : provides a single dedicated path for each connected device. Ports a socket for external devices to connect to the system unit.  Some ports connect directly to the system board, while others connect to cards that are inserted into slots on the system board. 30 Some ports are standard features of most computer systems, and others are more specialized: 1- Standard Ports • Universal serial bus (USB) ports can be used to connect several devices to the system unit , used to connect keyboards, mice, printers, storage devices, and a variety of specialty devices. A single USB port can be used to connect many USB devices to the system unit. • High Defi itio Multi edia I terfa e HDMI ports provide high-definition video and audio. • Thu der olt ports, provide high-speed connections. A single port can connect up to seven separate devices connected one to another. • Ether et ports are a high-speed networking port ,allows you to connect multiple computers for sharing files, or to a DSL or cable modem for high-speed Internet access. 2- Specialized Ports: • E ter al Serial Ad a ed Te h olog Atta h e t eSATA ports provide highspeed connections for external hard-disk drives, optical discs, and other large secondary storage devices. • Musi al i stru e t digital i terfa e MIDI port for connecting musical instruments like an electronic keyboard to a sound card. • Mi i Displa Port Mi iDP or DP ports are audiovisual ports typically used to connect large monitors. • VGA Video Graphi s Adapter a d DVI Digital Video I terfa e ports provide connections to analog and digital monitors, respectively. • FireWire ports provide high-speed connections to specialized FireWire devices such as camcorders and storage devices. Cables are used to connect exterior devices to the system unit via the ports. One end of the cable is attached to the device, and the other end has a connector that is attached to a matching connector on the port. Power Supply  Desktop computers have a power supply unit located within the system unit. - unit plugs into a standard wall outlet, converts AC to DC, and provides the power to drive all of the system unit components.  Laptops typically use AC adapters that are located outside the system unit. - AC adapters plug into a standard wall outlet, convert AC to DC, provide power to drive the system unit components, and can recharge the batteries.  Tablets and mobile devices use internal AC adapters that use a cable to connect to a standard wall outlet. - Some smartphones, use a wireless charging platform eliminating the cable. - Unlike most laptops, most tablets, mobile devices, and wearable computers can operate only using battery power. 31