Chapter 1: Motherboard and Peripherals

Transcription

1 Chapter 1: Motherboard and Peripherals Chipset Basic, Chipset Architecture, North / South Bridge / Hub Architecture: A chipset is a set of electronic components in an integrated circuit that manages the data flow between the processor, memory and peripherals. It is usually found in the motherboard of a computer. Processor AGP North Bridge RAM PCI South Bridge HDD ISA BIOS LAN SCSI Fig: Northbridge & Southbridge Architecture Northbridge 1. Northbridge is also called Memory Controller Hub (MCH) in Intel Systems. It is one of the two chips in the core logic chipset on the PC motherboard. 2. It handles communication between CPU, RAM, AGP or PCI Express and the Southbridge. 3. Some North-bridges also have the integrated Video controller called Graphics Memory Controller Hub (GMCH). 4. Since different processors and RAM require different signaling, a north-bridge will work with one or two types of CPU and only one type of RAM It provides the number, Speed, type of CPU, Size, type of RAM that can be used. 5. The north-bridge plays an important role in deciding how far a computer can be overclocked. 6. It uses a heat sink and some kind of cooling (Fan). South bridge 1. The Southbridge, also known as the I/O Controller Hub (ICH) 2. It is a chip that implements the "slower" capabilities of the motherboard in north bridge/south bridge chipset computer architecture. 1

2 Architecture of Intel chipset 945G 1. The Intel 945G chipset family includes 3 members 945G, 945P and 945TL. 2. It supports Intel new dual core Pentium. Processor & also supports Pentium 4HT technology processor. 3. It offers FSB speed up to 1066 MHz 4. 4GB dual channel DDR2 memory. 5. It also incorporates Intel graphic media accelerator integrated on board. 6. It uses ICH7 which is faster than ICH6. Features of ISA 1. Eight data lines. 2. Eight interrupt request levels address lines. 4. Enables to handle 1MB of memory. 5. It supports 3-4 DMA (Direct Memory Access) channels. Features of PCI-X bus: 1. Up to 133MHz bus speed bit bandwidth 3. 1 Gbps throughput 4. More efficient bus operation for easier interface. 5. Backward compatibility. Features PCI Express 1. Peripheral Component Interconnects (PCI) has 32 bit wide data. 2

3 2. It runs on 2.5GHz. 3. No priority queues. 4. Address / Data lines multiplexed. 5. Multi target, multi master 6. The maximum transfer rate is 16Gbps. Q. Explain BIOS with its any 3 functions. (1M Explanation, 3 Functions) Ans: Definition: Basic Input/output System, the BIOS, ROM BIOS, or System BIOS is a chip located on all motherboards that contain instructions and setup for how your system should boot and how it operates. The main function of BIOS in a computer is to offer a small library of basic input/output functions that are used to run and manage computer peripherals. Main functions that the BIOS perform include: A power-on self-test (POST) for all of the different hardware components in the system to make sure everything is working properly Activating other BIOS chips on different cards installed in the computer - For example, SCSI and graphics cards often have their own BIOS chips. Providing a set of low-level routines that the operating system uses to interface to different hardware devices - It is these routines that give the BIOS its name. They manage things like the keyboard, the screen, and the serial and parallel ports, especially when the computer is booting. Managing a collection of settings for the hard disks, clock, etc. The BIOS is special software that interfaces the major hardware components of your computer with the operating system. It is usually stored on a Flash memory chip on the motherboard, but sometimes the chip is another type of ROM. Concept of Cache Memory: Q. What is cache memory? What are its types? With the help of neat diagram explain the working principle of cache. 3

4 Cache memory is extremely fast memory that is built into a CPU, or located next to it on a separate chip. It supplies the processor with the most frequently requested data and instructions. A cache controller always tries to make sure that the data required by the processor in the next memory access is available in the cache memory. There are three types of cache memory: L1, L2 & L3 cache memory. L1 cache memory: 1. The L1 cache also called internal or integral cache is always a part of the processor chip. 2. L1 cache always runs at full processor speed. 3. It was the fastest cache in the system. 4. L1 cache was originally 8 KB. L2 cache memory: 1. The L2 cache originally called external cache because it was external to the processor chip when it was introduced. 2. It was present on the motherboard and used to run at CPU bus speed. 3. To improve the performance of the system, L2 cache was directly incorporated as part of the processor die. 4. L2 cache was originally 128 KB. L3 cache memory: 1. The L3 cache has been present in high end work stations and servers such as Xenon and Itanium. 2. Pentium 4 Extreme Edition was the first desktop PC processor with L3 cache. 3. Later Editions of same processor were introduced with larger L2 cache rather than L3 cache State characteristics of L2 cache 1. It is external to the processor core. 2. Same processor can be used with different L2 cache. 3. Larger L2 cache increases the performance of the system. 4. Cache performance can be measured in terms of Miss Rate, Hit, Time, miss Penalty. 5. Miss Rate = Fraction of memory references not found in cache 6. Hit Time = Time to deliver a line in the cache to the processor (includes time to determine whether the line is in the cache) 7. Miss Penalty = Additional time required because of a miss 4

5 Types of RAM. SRM (Static RAM): the content remains permanent as long as power is given to it. Once the information is written in any location is SRAM, it is preserved there. DRAM (dynamic RAM): DRAM stores each bit in a storage cell consisting of a capacitor and a transistor. Capacitors tend to lose their charge rather quickly; thus, the need for recharging or refreshing. Types of DRAM: 1. FPM (Fast Page Mode): It was traditional RAM for PC. It was mounted in single inline memory module (SIMM) of 2MB, 4MB, 8MB, 16MB, 32MB. 2. EDO (Extended Data Out): It is faster than FPM RAM. EDO have improvement in performance 2% to 5% compared with FPM. 3. ECC (Error Correcting Code): It is special error correcting RAM used in server. 4. SDRAM (Synchronous Dynamic RAM): SDRAM replaced DRAM, FPM, and EDO. SDRAM is an improvement because it synchronizes data transfer between the CPU and memory. SDRAM allows the CPU to process data while another process is being queued. Features of SDRAM: All SDRAM chips for desktop PC have 168 pins Speed of SDRAM is 100 MHz & 133 MHz Available in sizes 32MB, 64MB, 128MB, 256MB, 512MB, & 1GB Operating Voltage 3.3 V Architecture used Synchronous Operating Max Temperature is 85 o C It pre-fetches 1 bit at a time. DDR (Double Data Rate SDRAM): also called DDR1 SDRAM. DDR SDRAM (double data rate SDRAM) is synchronous dynamic RAM (SDRAM) that can theoretically improve memory clock speed to at least 200 MHz 5

6 Features of DDR SDRAM: All DDR RAM Chips have 184 pins. DDR RAM comes in different speeds i.e.100mhz, 133MHz, 166MHz, 200MHz DDR is twice as fast as SDRAM Operating Voltage 2.5 V Architecture used is Source Synchronous (it refers to the technique of having the transmitting device send a clock signal along with the data signals.) Operating Max Temperature 85 o C It Pre-fetches 2 bit at a time DDR2 (Double Data Rate 2 SDRAM): Features of DDR2: The DDR2 RAM chip has 240 pins DDR2 operate at data rates of 400MHz, 533MHz, 667MHz, & above Higher Bandwidth Lower power 1.8V Architecture used source synchronous It pre-fetches 4 bits at a time Operating Max Temperature 95 o C DDR3 (Double Data Rate 3 RAM): Features of DDR3: Introduction to asynchronous RESET pin. Support system level same delay compensation. On DIMM (dual in-line memory module) mirror friendly DRAM pin out. Introduction of CWL (CAS Write Latency) per Speed bin. On-die I/O calibration engine. READ & WRITE calibration. It works on very low power i.e.1.5v DDR3 operate at data rates of 800MHz, 1066MHz, 1333MHZ, 1600MHz, & above. It pre-fetches 8 bits at a time. 6

7 Construction of CD, DVD ROM: A DVD is composed of several layers of plastic, totaling about 1.2 millimeters thick. Each layer is created by injection molding polycarbonate plastic. This process forms a disc that has microscopic Lands/Pits arranged as a single, continuous and extremely long spiral track of data. Once the clear pieces of polycarbonate are forms, a thin reflective layer is sputtered onto the disc, covering the bumps. Aluminum is used behind the inner layers, but a semi-reflective gold layer is used for the outer layers, allowing the laser to focus through the outer and onto the inner layers. After all of the layers are made, each one is coated with lacquer, squeezed together and cured under infrared light. Construction of CD/DVD ROM Drive: CDROM DRIVE Compact Disc Read only Memory Use to read CDROM Connected to computer via IDE (ATA), SCSI, USB interface the basic components of the CD-ROM drive are the following: 1. Optical head 2. Turntable 3. Computer interface section 4. Microprocessor based control system 7

8 The optical head contains the circuitry to read the data from the disc. This unit usually consists of four main subassemblies; (1) The laser, used to generate a light beam; (2) A lens system, to focus the laser beam on the disc and to direct the reflected light to the photo detector; (3) A series of servomotors that controls the position of the laser and lenses to ensure proper racking and focus; and (4) A photo detector that evaluates the reflected light and converts the light to electrical impulses. TURNTABLE The turntable rotates the disc and is driven by a servomotor. Since the data is written in a continuous spiral, the speed of the turntable must be adjustable so that the information passes over the optical head at a constant speed. The audio CD requires a speed of 1.3meters per second. This speed was adapted for use in computer applications, but proved to be extremely slow when compared to the processing and data transfer speeds of modem computers. The 2 X CD-ROM drives doubled the speed the data track passed over the optical head. The 4X, 6X, and 8X CD-ROM drives spin the disc even faster. The speed multiplication factor is based on the original speed of 1.3 meters per second. INTERFACE SECTION The interface section provides for the transfer of data between the computer and the CD-ROM drive. Many CD-ROM drives are manufactured with the small computer systems interface (SCSI), although some proprietary interface units are available. CD CONTROLLER The CD controller processes the signals received from the optical head, attempts to correct any errors in the data, and controls the speed of the turntable. The information from the photodiodes that is received by the controller is still encoded in eight-to-fourteen modulation (EFM) data. The decoding of EFM data is done by the microprocessor. The code addresses a ROM that contains the proper byte for the encoded data. The output of the ROM is stored in a RAM where it is checked for errors. CD/DVD Recording Mechanism:- The CD recording drive has a laser unit, which heats the organic layer which makes the hole (called as pit ) Information recorded on CD using a series of pits. These pits are also called as bumps. The unmarked areas between pits are called lands. Lands are flat surface; the information is stored permanently as pits and land on the CD. Light reflected from pit to land or land to pit transition the intensity of reflected light changes.(logic 1) No change in intensity of light from pit of land is logic 0. 8

9 EMF (Eight to Fourteen modulations) is an encoding technique used by CD. Data is broken into 8 bit blocks and each block is translated into 14 bit codeword using predefine lookup table. The 14 bit codeword chosen so that binary ones are always separated by minimum 2 and maximum 10 binary zeros. LCD Monitor: LCD module with 4 lamps (backlight) Inverter Interface Board Power Control Board AC Power R, G, B, H/V Sync D-Sub Functions of block: Interface Board: The function of interface board is to convert an input signal into a digital RGB signal. Output data are sent to the LCD module. Control Board: It controls the user operation. It has two parts, push button & an LED. a) Push button: It is a simple switch function, pressing it for ON to do the auto adjustment function, releasing it for OFF to do nothing. b) LED: It indicates the DPMS (Display Power Management Signaling) status of the LCD monitor. Inverter: The main function of the inverter is to convert AC voltage in required DC voltage for LCD module & interface board. LCD module: The function of this is to display image, data or text on screen. It is used to control of the backlight of the LCD. Working Principle of LCD The main principle behind liquid crystal molecules is that when an electric current is applied to them, they tend to untwist. 9

10 Liquid Crystal Display technology works by blocking light. LCD is made up of two pieces of polarized glass (also called substrate) that contain a liquid crystal material between them. A backlight creates light that passes through the first substrate. This causes a change in the light angle passing through them. At the same time, electrical currents cause the liquid crystal molecules to align allow varying levels of light to pass through to the second substrate & create the color images. Passive-matrix vs. active-matrix driving of LCD Monitors. Passive Matrix: Passive matrix LCDs use a simple grid to supply the charge to a particular pixel on the display. The liquid crystal material is sandwiched between the two glass substrates and a polarizing film is added to the outer side of each substrate. To turn on a pixel, the integrated circuit sends a charge down the correct column of one substrate and a ground activated on the correct row of the other. The row and column intersect at the designated pixel, and that delivers the voltage to untwist the liquid crystals at that pixel. To address a pixel the column containing the pixel is sent a charge; the corresponding row is connected to ground. When sufficient voltage is placed across the pixel, the liquid crystal molecules align parallel to the electric field. 10

11 In passive matrix LCDs (PMLCDs) there are no switching devices and each pixel is addressed for more than one frame time. Active Matrix LCD In active matrix LCDs, a switching device and a storage capacitor are integrated at the each cross point of the electrodes. The active addressing removes the multiplexing limitations by incorporating an active switching element. In contrast to passive matrix LCDs, active matrix LCDs has no inherent limitation in the number of scan lines, and they present fewer cross talk issues. There are many kinds of AMLCD. For their integrated switching devices most use transistors made of deposited thin films, which are therefore called thin-film transistors (TFTs). Parameters Active Matrix Passive Matrix Contrast Good(100+) Poor(10-20) Viewing Scale Wide Limited Gray Scale Response time Fast(<50ms) Slow( ms) Multiplex ratio > Manufacturabilit Complex Simple y Cost High Moderate Used in Color monitor Monochrome monitor Advantages of LCD display over CRT display: 1. LCD monitor consumes less power: An average 19 inches, LCD uses 45 watts of electricity while the 19 inches CRT uses 100 watts of electricity. 2. LCD monitors are smaller, thinner& weight half as much as CRT, 3. An LCD monitors tilt, height, & orientation from horizontal to vertical can all be adjusted easily. 4. LCD monitors don t produce the flickers that CRT s do. I.e. generated less eye strain. Important characteristics: 1. Dot Pitch: Distance between two adjacent pixel centers. 2. Resolution: It is number of horizontal & vertical pixels. 11

12 3. Refresh rate: The refresh rate is the number of times in a second that display hardware draws the data. 4. Response time: The minimum time necessary change in pixel color or brightness. 5. Viewable size: CRT monitor gives viewable size in diagonal measures from 15 inch to 42 inch. 6. Color Support: Number of types of color is supported. Advantages of CRT display over LCD display: 1. Resolution & aspect ratio: They operate at any resolution, geometric & aspect ratio without the need for rescaling the image. 2. Highest Resolution: CRT runs at highest pixel resolution. 3. Black level & Contrast: Suitable for used in dark dim light environment. 4. Color & gray scale accuracy: CRT produced the very best color & gray scale & are reference standard for all professional calibration. 5. Cost: CRT is less expensive than LCD. KEYBOARD: A keyboard is a typewriter-style device, which uses an arrangement of buttons or keys, to act as electronic switches. Different types of key Switches in Keyboard: 1. Capacitive Key Switch 2. Membrane Key Switch 3. Rubber Dome Key Switch 4. Hall Effect Key Switch 5. Opto-Electronic Key Switch 6. Mechanical Key Switch a. Working principle of Membrane key switch: It is a multi-layer plastic or rubber assembly. It is used as keyboard in video game machines, calculators, medical instruments, cash registers etc. 12

13 Two rubber or plastic sheets are used as row conductor sheet & column conductor sheet. Row & column line are made on the plastic or rubber sheet using silver or some other conductor ink. b. Working principle of Mechanical Key switch: Two metal pieces or contacts are kept in open position & moved into closed position when switch is pressed. When the switch is in normal position the contact is open, when the switch is pushed the contact closes, & the closure is sensed by the keyboard interface. After some use contacts become oxidized or dirty & make the switch useless. Gold plating on these contacts is done to improve the life span of the switch. Normal life span of high quality switches is about 1 million keystrokes. 13

14 MOUSE: a. Optical Mouse: 1. In this type of mouse, a light source & photo detector is used with a special mouse pad. 2. When the optical mouse is moved on this special pad, light from the light source gets reflected from the pad &special photo detector inside the mouse detects the horizontal & vertical movements. 3. Two photo detectors are there, among that one of the photo detectors is used to detect vertical movement of the cursor on the screen & the other is used to detect the horizontal movement of the cursor on the screen. 4. The movement of the cursor on the screen depends on the number of the signals that is passed to the PC through the wire connected with the mouse. The PC, in turn, passes them to the mouse driver software which then converts the distance, & speed required for the movement of the screen cursor. PRINTERS: Printers are Output devices used to prepare permanent Output devices on paper. Printers can be divided into two main categories: Impact Printers: In this hammers or pins strike against a ribbon and paper to print the text. This mechanism is known as electro-mechanical mechanism. They are of two types. Non-Impact Printers: There printers use non-impact technology such as ink-jet or laser technology. There printers provide better quality of O/P at higher speed. Q. State any four printer characteristics. (For any 4 characteristics ½M) Printer type: Impact or Non-impact, laser or Inkjet 1. Resolution : specified in dpi 2. Print direction: One directional or Bi directional 3. Input Buffer : size in KB or MB 4. Printer Speed : in CPM, LPM or PPM 5. Interface : Serial or parallel/usb 14

15 DOT MATRIX PRINTERS: A Dot Matrix Printer or Impact Matrix Printer refers to a type of computer printer with a print head that runs back and forth on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like a typewriter. Unlike a typewriter or daisy wheel printer, letters are drawn out of a dot matrix, and thus, varied fonts and arbitrary graphics can be produced. Block Diagram of Dot Matrix Printer Working of DOT matrix printer: 1. PC sends a series of ASCII code & some printer movement information to the printer through a serial or parallel cable. 2. The ASCII codes received by the printer are stored inside a buffer. i.e. RAM 3. The processor inside printer select particular dot pattern & stored into bitmap table (ROM). 4. The print head consists of pins which are arranged in a vertical column. 5. The pins are operated electromagnetically & the character to be printer has dots in certain position of the matrix. 6. The required dots for a column are formed by striking appropriates pins then the printer head moves to the next column. Characteristics of Dot-matrix printer: It is an impact printer, where printer head touches the paper with an inked ribbon The quality of the image is determined by the dots per inch. Its speed is measured with respect to characters per second(cps) It s quality of printing is not as good as other non impact printers The Mechanical movements are more when compared to other printer and also noisy. Most of the Dot Matrix printers are with parallel ports (Centronics) 15

16 Advantages: 1. It can print on multi-part stationery or make carbon copies. 2. Impact printers have one of the lowest printing costs per page. 3. They are able to use continuous paper rather than requiring individual sheets. 4. The ink ribbon also does not easily dry out. Disadvantages: 1. Impact printers are usually noisy. 2. They can only print low resolution graphics, with limited color performance, limited quality and comparatively low speed. 3. They are prone to bent pins (and therefore a destroyed print head) caused by printing a character half-on and half-off the label. Specification of Dot matrix Printer: 1. Speed of a Dot matrix Printer is defined in cps ( characters per second) for eg., characters per second 2. Type of paper used can be continuous paper or separate paper 3. Print quality depends on number of print pins (from 9 to 24pins) 4. Type of interface is a parallel interface or serial interface (LPT or COM ports) 5. Line width is generally 80 characters, or columns, with some dot matrix printers being capable of 132-character lines. INK JET PRINTERS: Working of Inkjet printer: 1. An ink filled cartridge is attached to the head. 2. The print head is made up of small ink filled chamber, each attached to a nozzle which is smaller than human hair. 3. Electrical pulse flows through heating elements which is usually a resister located at the back of the each chamber. 4. The heat generated by the register heats thin layer of ink resulting in boiling of ink & thus formation of a small bubble of vapor. 16

17 5. This bubble expands & a droplet of ink falls on the paper. Thus resulting in the formation of character of these drops. Q. Give any four disadvantages of Ink-jet Printer. (Any 4 points, 2 Marks) 1. Inkjet printers require periodic maintenance or else the ink gets logged in the nozzle. 2. They require special paper with controlled absorbency for best results 3. Ink cartridges are costly than ribbon and don t last longer. 4. It is costly than dot matrix printer. LASER PRINTER: A type of printer that utilizes a laser beam to produce an image on a drum. The light of the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum. Finally, the toner is transferred to the paper through a combination of heat and pressure. The 6 steps laser printing process 1. Cleaning The Photosensitive drum is cleaned before it can take on a new image 2. Conditioning or Charging To make the drum receptive to new images, it must be charged. The EP drum is given a negative charge by the primary corona wire around -600 and volts 3. Writing - A laser beam is use to write to the EP drum causing dots on the drum to lose some of the negative charge and become relatively positive charge 4. Developing - A toner is transferred from the toner cylinder to the EP drum by attracting the area of the drum that has a Relative positive charge 5. Transferring - The transfer corona wire puts a highly positive charge on the paper once the paper has a positive charge the negatively charge toner particle leaps from the drum into the paper 17

18 6. Fusing - The compression roller and fusing roller press and melts the toner into the paper the fuser gets very hot. Specifications of Laser Printer: 1. Print speed: up to 19PPM 2. Print technology: Laser 3. Print quality: 1200 x 1200 DPI (B/W) 4. Memory: 8 MB 5. Interface: USB 6. Power consumption: 320W when operational 7. Graphics Resolution: 300 to 2400 DPI 8. Media supported: Paper, Envelopes, and Transparencies Q. List any four advantages of Laser Printer over Dot Matrix printer. (Any 4 points, 2 Marks) 1. It is a non impact printer. 2. It is not noisy. 3. Printing speed is fast. 4. Printing quality is very good. Characteristics: 1. Speed: Given in Pages per Minute (PPM) the higher the PPM the more pages they can print. Most ink-jet printers offer different speeds depending on the quality of print desired. 2. Print quality: Determined by the DPI (Dot Per Inch) Example 4880 x 2440 DPI (Vertical and Horizontal DPI) 3. Ink: Laser Printers use Toner Cartridges 18

19 SCANNER: Working of flat bed scanner: 1. Light source illuminates piece of paper face down against glass window above the scanning mechanism. 2. Motor moves the scan head beneath the page. 3. The scan head captures light reflected from individual areas of the page. 4. Reflection takes through system of mirrors. 5. Lens focuses the reflected beam of light on light sensitive diodes. 6. The diodes generate electric current corresponding to the amount of reflected light. 7. White spaces reflect maximum light, which generates maximum voltage. 8. ADC converts each analog signal voltage to digital pixel representing the scanned area. 9. For Monochrome Scanner 1 bit per pixel is stored-either on or off. 10. For Color Scanner, the scan head makes three passes under the images. 11. Reflected light on each pass is directed through red, green and blue filter before it strikes the original image. 12. Signals from the three passes are converted into digital information and stored to represented, green or blue color value of the scanned area on the page. This digital information is sent to the software in the PC, where data is stored in a format on which OCR can work. 19