Motherboards Overview In this chapter you will learn

Motherboards

Overview In this chapter, you will learn to Explain how motherboards work Identify the types of motherboards Explain chipset varieties

Motherboard Provides foundation for PC Every piece of H/W , from CPU to expansion card directly Example? or indirectly plugs into it. Example? 3

Motherboards are officially printed circuit boards (PCBs) PCBs come in multiple layers with highways of wires (bus systems) in the layers These highways of wires are called traces Holds the vast majority of the ports used by peripherals and it distributes powers from power supply. 4

Motherboard Characteristics Three interrelated characteristics define modern motherboards : Form Factor defines › Physical Size of the motherboard. › General location of components and parts. Chipset defines › Type of processor and RAM supported. › Determine the internal and external devices supported by the motherboard. Built-in components › Determine the core functionality of the system.

Form Factors Industry standardized shapes and layouts that enable motherboards to work with cases and power supplies. A single form factor applies to all 3 components (motherboard, power supply, and case). You need to install a motherboard in a case designed to fit it, so ports and slot opening in the back fit correctly Power supply and motherboard need matching connectors. 6

Form Factors The PC industry construct a number of form factors over the years with name such as: ATX BTX And others. 7

AT Form Factor Used P 8 and P 9 connectors to power the motherboard Single keyboard DIN or (PS1) connector Lack of external ports Distinguished by position of the keyboard plug and power socket Now: obsolete Has a few size variations: Baby AT is the most common (Pentium) Full AT LPX and NLX. 8

Baby AT Motherboard Single keyboard DIN connector Lack of external ports Power supply connector Small size 9

ATX Form Factor Created in 1995 Improves four main areas over AT. Replace DIN port in AT with rear panel that has all necessary ports built in. Better air movement Easier access of RAM and CPU Enhanced performance: by placing RAM closer Northbridge and CPU. Uses soft power to turn PC on/off through software. to 10

ATX Form Factor Uses Single 20 -pin P 1 power connector instead of P 8 and P 9. Variations (smaller versions of ATX): Micro ATX and Flex ATX. Many techs and web sites use the term mini-ATX to describe these boards 11

ATX Form Factor Each main type of form factor requires its own cases. AT Motherboard go into AT cases. NLX Motherboard go into NLX cases. Therefore, you can not replace one form factor with another without purchasing a new case. Exception: Exception larger form factor ATX cases can handle any smaller-sized form factor motherboard. 12

ATX Motherboard Parts

AT and ATX Boards 14

Power Supply Connectors 15

System Board (Pentium) Baby AT: 1 - PS connector. 2 - single DIN 3 - Size 16

System Board (Pentium II) ATX: 1 - PS connector. 2 - rear panel 17

BTX Form Factor BTX (Balanced Technology Extended) Due to heat, cooler form factors needed Three subtypes of BTX › BTX designed to replace ATX › micro. BTX designed to replace micro. ATX › pico. BTX designed to replace Flex. ATX Its look like ATX but you can not put a BTX motherboard in an ATX case. Why? BTX does not change the power connection, so there is no such thing as a BTX power supply. 18

BTX Form Factor & Thermal Unit CPU moved to front of Motherboard 19

The Chipset Serves as electronic interfaces through which the (CPU, RAM, and input/output devices) interact. Like what? RAM I/O Chipsets CPU Several Chipset Varies in feature, performance and stability. Composed of : Northbridge high speed interfaces like video card RAM and Southbridge low speed devices such as USB controller and hard drive controller keyboard controller. 20

The Chipset Northbridge: Helps the CPU work with RAM and video (on Intel-based systems). Communicates with video card on newer AMD systems. Why? Therefore they do a lot and get hot so they get their own heat sink and fan assembly. Southbridge: handles some expansion devices and mass storage drives. Don’t need extra cooling. Modern Southbridge do not support old devices (floppy drive, parallel port, modem, . . ). A third chip called Super I/O chip (not part of chipset) chipset handle them. 21

The Chipset Not always called Northbridge and Southbridge Intel-based motherboards may refer to them as: Memory Controller Hub (MCH) for Northbridge and I/O Controller Hub (ICH) for Southbridge. 22

The Chipset The system ROM chip provides part of the BIOS for the chipset. It is not sufficient. You have to load the proper drivers for the specific OS to support all features of today’s chipsets. All motherboard ship with a CD-ROM disc with drivers. 23

Chip Set Manufacturers Some of the companies produce chipset designed for both Intel and AMD CPUs whereas others choose one or the other company to support. Intel Corporation AMD, Inc. VIA Technology, Inc. NVDIA corporation Si. S 24

How it all connects together backside bus L 2 Cache Pentium CPU (in the CPU housing – on die) 32 bit address bus 64 bit data bus RAM memory bus HDD EIDE CD/DVD frontside bus L 1 cache North Bridge The Chipset (Memory Controller) extends the bus to AGP bus every device on the PC. AGP scanner PCI South Bridge PCI bus sound ISA bus keyboard mouse modem FDD ISA BIOS 25

Motherboard Components Connections and capabilities of a motherboard sometimes differ from its chipset. How? Not all chipset features may be supported with ports (for cost savings) Also a motherboard maker may choose to install extra features USB / Fire. Wire page 237 (exercise) exercise Sound page 238 (exercise) exercise RAID page 238 (exercise) exercise AMR/CNR page 238 (exercise) exercise 26

BIOS and CMOS 27

Overview In this chapter, you will learn to Explain Read Only Memory Explain the function of BIOS Distinguish among various CMOS setup utility options Describe BIOS and device drivers

What is (ROM)? b b b Read Only Memory chips that contain data, instructions, or information that is recorded permanently. b Data can only be read, cannot be modified b Nonvolatile — Contents not lost when the computer is turned off Program stored on ROM are known as firmware not a Software.

Read Only Memory (ROM) b ROM have different type: b ROM b Programmable Read-Only Memory (only once) b Blank ROM on which you can place items permanently b EPROM Erasable PROM by Ultraviolet (every time you want) EEPROM b Electrically Erasable PROM b A type of PROM containing microcode that a programmer can erase using electricity. b b

What is Flash Memory? b b b Variation of EEPROM Also called flash ROM or flash RAM Nonvolatile memory that can be erased electronically and reprogrammed. Stores data and programs on many handheld computers and devices such as Camera and mobile phone. Flash memory cards store flash memory on removable devices instead of chips

We Need to Talk Placing a number of components into a computer is useless if CPU can not communicate with them. 32

Northbridge & Southbridge Bridges (North, South) connect the devices CPU uses address bus to talk to devices But , How does it know what to say to them? Keyboard controller chip 33

Basic Input Output Services A special kind of Program is i required to enable the CPU to talk to other devices These programs are collectively known as the basic input/output service (BIOS) A Flash ROM chip stores these programs Why? When CPU wants to talk to KB controller, it goes to BIOS ROM chip to access the proper program. Similar to codebook 34

BIOS Basic Input Output Services Permanently stored on ROM chip called System ROM or System BIOS Contains small programs - each program is called a service- that enable CPU to Communicate with the devices (keyboard, floppy, hard drive, monitor, …) They are necessary to start the computer load the operating system and other files when you first turn on the computer 35

BIOS 36

ROM BIOS There is One ROM chip on the system board that contains BIOS. Modern motherboards use Flash ROM (you can change the contents through a very specific process called “flashing the ROM”) ROM Read about it in book P 180 There exists hundreds of little services (2 to 30 lines of code each)for communicating with floppy drives, hard drives, … 37

System BIOS ROM chips can store 2 MB although only 65, 536 bytes system are used to store system BIOS. Every system BIOS has two types of hardware to support. First: First All hardware that never changes. Ex: Ex KB, PC speaker. You cannot change keyboard controller chip. Second: Second All hardware that might change. Ex: Ex RAM (you could add RAM), hard drives (replacing/ adding). The system ROM stores the BIOS for them, but it needs another place to store information about the specific details 38 of them CMOS

CMOS A separate memory chip, called Complementary Metal. Oxide Semiconductor (CMOS) chip stores the information that describes specific device parameters. CMOS does not store programs, only data that is read by BIOS to be able to talk to the changeable hardware. CMOS also acts as a clock to keep date and time Years ago: CMOS was in separate chip. Today: CMOS is built into Southbridge. 39

CMOS can store up to 64 KB of data but usually only uses about 128 bytes CMOS chip is volatile (kept alive by battery). This way the information contained in the CMOS are always present even if the computer power is turned off. 40

CMOS Stores only changeable data. Customizable via SETUP program. If data in CMOS about certain hardware is different from its actual specs, PC can not access that hardware. If you change one of changeable devices, parameters have to be changed in CMOS how to change data on CMOS? 41

CMOS SETUP Program Special program that allows you to access and update CMOS data Stored on system ROM (BIOS) BIOS Companies that write the BIOS and how to access CMOS at boot: Phoenix Technologies - Ctrl Alt Esc Award Software - uses DEL key American Megatrends (AMI) - DEL key Other key combinations are: Ctrl Alt Ins, Ctrl A, Ctrl S, Ctrl F 1, or F 10 42

Accessing Award SETUP 43

CMOS setup program 44

CMOS setup program Exercise: how to access CMOS setup on your PC and what are the available options? Caution: Caution it is perfectly fine to access the CMOS setup program, but do not make changes unless you fully understand the system 45

BIOS and device drivers PC designers understood that they could not anticipate every new type of H/W. Therefore, they gave us ways to add programs for new devices other than on the BIOS. It is called BYOB (Bring Your Own BIOS) BIOS Ex: Mice, Sound cards, …. Two ways to BYOB: Option ROM (hardware solution) and device driver (software solution) 46

Option ROM Embedded the BIOS in a ROM on the hardware device itself. Today only video card contains its own BIOS. Most devices use more flexible software method (device derivers). 47

Device drivers A device driver is a file that contains the BIOS commands necessary to communicate with the devices they support stored on the PC’s hard drive. Operating system loads these drivers into RAM when booting They come with the device - in a CD- when you buy it. The generic name for CD is installation disc 48

Registry A special database –used by windows- that stores everything you want to know about your system, including device drivers. Use device manager utility to access registry. You can manually change/remove and drivers Exercise: Exercise how to use device manager? 49

Device Manger 50

POST The power-on self test (POST) is a special program stored on the ROM chip (BIOS) Initiated when the computer is turned on or is reset Checks out the system every time the computer boots POST program sends out a standard command that says to all the devices “check yourselves out”. All standard devices run their own internal diagnostics. Quality? PCs convey POST information to user in two ways: beep codes or text message (more useful) Exercise: study more about beep codes and text Exercise 51 message

System ROM Responsibility System ROM contains: BIOS routines CMOS setup program POST 52

Basic Boot Process (Step) Once the power is turned on, the PC “pulls itself up by its bootstraps” First component to wake up is the CPU By reads a special wire called power good wire once the power supply provides the certain voltage to the CPU Built in memory address is sent on address bus. This address represent the first line of POST program on the system ROM POST is run If problem happen beep code or text message displayed. 53

Boot Process After POST finishes, it passes control to last BIOS function: the bootstrap loader Its job is to find the operating system. The bootstrap loader loads the operating system from the boot sector (In hard drive implementation chapter) Searches the floppy, CD-ROM, or the hard drive Boot order set in CMOS It reads CMOS to tell it where to look first for operating system (boot order). order 54

Boot Process If the device is bootable (called system disk), its boot sector will contain special programming designed to tell the system where to locate the operating system. If bootstrap loader locates a good boot sector, it passes control to operating system and removes itself from memory. Otherwise it goes to next device specified in CMOS. 55

Care and Feeding of CMOS If CMOS battery run out of charge, you lose CMOS information and computer will not boot. Any PC made after 2002 will boot to factory default if the CMOS clears but you will still get error at boot CMOS configuration mismatch CMOS date/time not set No boot device available CMOS battery state low. HOW to replace it? 56

Care and Feeding of CMOS Common reasons for losing CMOS data On-board battery runs out Pulling and inserting cards Touching the motherboard Dropping something on the motherboard Dirt on the motherboard Faulty power supplies 57

Fix Problem To fix these problems: Have CMOS setting memorized Replace the battery. Compare current settings to backup copy CMOS save and restore program CMOSSAVE. 58

Clearing CMOS Settings To clear the CMOS settings, place the shunt on the CMOS jumper Resets to factory settings Resets password 59