1. Motherboard

2. Introduction the large circuit board inside your computer's case. Sometimes called the system board, the logic board, the baseboard or the planar board. Everything connected to the computer system, plugs either directly or indirectly into the motherboard Some therefore think of it as the central nervous system of the computer

3. What do we mean? The Central Processing Unit (CPU) sits on the motherboard The motherboard also contains the Basic Input/ Output System (BIOS) chip and the CMOS Setup information. It has expansion slots for installing different adapter cards e.g. video card, sound card, Network Interface Card (NIC) and modem. This circuit board provides a connector for the keyboard as well as housing the keyboard controller chip. It has the system's Random Access Memory (RAM) slots, provides the system's chipset, controllers and the bus system

4. Types of Motherboards Non-integrated motherboard Integrated/embedded motherboard

5. Non- Integrated Motherboards Non-Integrated Motherboards have assemblies installed as expansion boards. The assemblies mentioned above include the I/O Port connectors (serial and parallel ports), hard drive connectors or paddle boards, floppy controllers and connectors, joystick connections... Most of the older motherboards were Non- Integrated.

6. Advantages of Non- Integrated Motherboards Mainly lies in cost.. i.e. The individual motherboard is relatively cheap to produce. should something go wrong with the individual assemblies, such as a bent or broken pin in a connector, or a defective controller chip, one could repair the problem by replacing the individual expansion card at a relatively cheaper cost than to replace the whole board

7. Disadvantage of Non-Integrated Motherboards Main disadvantage with this board is that it takes up one or more of the motherboard's expansion slots and reduces the amount of free space inside your computer's case, which would also limit expansion As well, because of the cost of manufacturing, testing and installing the expansion boards individually, there's an added cost to the overall computer system.

8. Integrated Motherboards Some of the later 486 system boards began to integrate some of these assemblies right onto the circuit board i.e. they are installed or built right onto the board The serial and parallel ports, the IDE and floppy drive, and joystick all connect directly to the motherboard. Other technologies integrated included video, sound, networking and modems right onto the system board.

9. Advantage of Integrated Motherboards Cost and affordability is a concern for any manufacturer. Make your product more affordable, and more people will buy it, creating a larger market and increased sales. This is actually the whole idea behind the integrated motherboards Reduction in cost - there's less material involved, less installation, and testing can all be done at the same time Better compatibility - the more things that are done by a single chip or group of chips from one manufacturer, the simpler the design is. Less chance of a problem - integrated assemblies are generally quite stable and even though problems occur, they tend to be rare. Integration also frees up some space inside the case and allows for better accessibility and airflow

10. Downside of Integrated Motherboards What happens if one of the embedded technologies gives out or there is a controller failure or broken pin? The solution would be to either repair it, which is quite expensive or to replace the motherboard. Some manufacturer have provision to upgrade or bypass a particular feature by installing an adapter card and disabling the embedded device. There are, however, problems with this: An ordinary user might have difficulties with disabling the current assembly. Some are disabled as soon as you install another device (such as a video card in an AGP slot). Others have to be disabled through software setup programs, or in your system's CMOS setup, or by setting jumpers on the motherboard itself

11. Downside of Integrated Motherboards ctd. Is it possible to upgrade to the device? Is there a list of the compatible devices? A lot of embedded system boards can be fussy about the model and manufacturer of the device you're using to replace an embedded feature. Is there room for the upgrade? Eg. embedded video technology has 4 megabytes of video RAM, upgradeable to, say 12MB. What this generally means is that there is 4MB of Video RAM, which is faster than regular system RAM and when upgraded to 12 MB, it will use 8MB of the system's RAM Newer video technology now uses regular system RAM instead of faster VRAM, and the 64 MB computer now has only 56 MB of memory, because 8MB has been allocated to video

12. Motherboard Components Here, we identify the various components found on the motherboard plus a brief description of each. Motherboards vary, one may find more or fewer chips or devices on your board, depending on its age and level of integration. However, these are the most common items found on a typical modern motherboard. Printed Circuit Board Processor Sockets or Slots Memory Sockets Cache Sockets I/O Bus Slots Power Connector(s) Voltage Regulators Capacitors Keyboard and Mouse Connectors Keyboard Controller Real-Time Clock and CMOS Memory Chip Super I/O Controller BIOS Chips Battery Jumpers Ports and Headers Pin Connectors System Chipsets and Controllers

14. Printed Circuit Board The motherboards is essentially a multiple layer printed circuit boards, also called PCBs. The physical board we see is actually a sandwich of several thinner layers, each containing some of the circuitry required to connect the various components on the board At one time this was expensive, difficult-to- manufacture technology, but time and automation has reduced this complexity to the point where the board itself is a minor component of overall cost. It is important to note that thin boards are subject to damage from flexing when inserting peripherals Rule of thumb: the thicker the board, the better.

15. Processor Sockets The motherboard has one or more sockets or slots to hold the processor(s). Single-processor motherboards are common, but dual processor and quad processor boards can be found. (Quad boards often use special, proprietary designs employing riser cards.) The type of socket or slot used dictates the type of processor (and in some cases the speed) that can be used by the motherboard. Most modern motherboards that have a socket use the ZIF (zero insertion force) style socket, which allows the processor to be inserted or removed from the motherboard by using a lever that tightens or loosens the processor's pins in the socket. This is a vast improvement over the older style sockets, which required you to exert considerable force on the surface of a delicate (and expensive) processor, just to get it into the motherboard

16. Memory Sockets Most motherboards have between 2 and 8 sockets for memory. These are either SIMMs (single inline memory modules) or DIMMs (dual inline memory modules) These sockets are labelled "SIMM0" through "SIMM7" or "DIMM1" through "DIMM3", etc. The sockets are almost always filled starting with the lowest numbered socket first. Most Pentium class or higher motherboards require SIMMs to be inserted in pairs, but DIMMs may be inserted individually

17. Cache Sockets Virtually all newer 486 or Pentium class motherboards come with either integrated secondary cache or sockets for secondary cache to be inserted. Also called "Level 2" or "L2" cache, secondary cache is high-speed memory that is used to buffer processor requests to the regular system memory. Either 256 KB or 512 KB of cache is most common, with larger sizes such as 1 MB and higher now coming onto the market. Motherboards for Pentium Pro and Pentium II PCs don't have level 2 cache on them; it is already integrated into the processor itself for the Pentium Pro Motherboards typically have either cache chips soldered directly into the board, sockets for cache chips, or a socket for COASt, or "cache on a stick". This socket is sometimes called a CELP ("card edge low profile").

18. I/O Bus Slots All motherboards have one or more system I/O buses, which are used to expand the computer's capabilities. The slots in the back of the machine are where expansion cards are placed (like your video card, sound card, network card, etc.) 3 types of slots: ISA (Industry Standard Architecture) bus slot, PCI (Peripheral Component Interconnect) bus slot and an AGP (Accelerated Graphics Port) slot. The first bus slot, ISA; most PCs have 3 or 4 of these. These slots have two connected sections and start about a half-inch from the back of the motherboard, extending to around its middle. This is the oldest (and slowest) bus type and is used for cards that don't require a lot of speed: for example, sound cards and modems. Older systems (generally made well before 1990) may have ISA slots with only a single connector piece on each; these are 8-bit ISA slots and will (of course) only support 8-bit ISA cards.

19. I/O Bus Slots ctd Pentium systems and newer 486-class motherboards also have PCI bus slots, again, usually 3 or 4. They are distinguished from ISA slots in two ways. First, they are shorter, and second, they are offset from the back edge of the motherboard by about an inch. PCI is a high-speed bus used for devices like video cards, hard disk controllers, and high-speed network cards. Newer PCs add another, new connector to the motherboard: AGP slot. This is not really a bus, but is a single-device port used for high-performance graphics. The AGP slot looks similar to a PCI slot, except that it is offset further from the back edge of the motherboard. Some motherboards incorporate a so-called "shared" ISA and PCI slot. This is a single slot that can take either type of card, but that isn't possible because the two slot types are physically incompatible. In order to save space while maximizing the number of expansion slots, some designers put an ISA slot on the board right next to a PCI slot; you then have the choice to use either the ISA or the PCI slot, but not both. This design is possible because ISA cards mount on the left-hand side of a slot position, while PCI slots mount on the right-hand side.

20. Power Connector(s) The motherboard has a socket to attach the power cables coming from the power supply. As discussed in the power supply chapter ATX forms factor motherboards and power supplies use a single, keyed 20-wire motherboard power cable. All others use a pair of 6-wire cables. The cables are connected to the motherboard so that the black wires (grounds) are together in the middle. This connector is usually found near the back right-hand side of the motherboard, near the power supply.

21. Voltage Regulators The advent of processors and other devices running at different voltages--in the "old days" they all used to run at the 5V provided by a standard power supply--has led to the necessity of one or more voltage regulators on most modern motherboards. These regulators reduce the 5V signal to those voltages typically needed by processors: 3.3V or lower. The voltage regulator can normally be identified by the large heatsinks that are placed on it; voltage conversion generates a great deal of heat. The regulator is controlled via processor voltage jumpers, which are set to the appropriate voltage for the processor being used. On many motherboards the cooling level of the entire system case is important to ensuring that the voltage regulators are cooled satisfactorily. Overheating regulators can cause lockups and other problems.

22. Capacitors Capacitors are electrical components that are used to filter and smooth signals on the motherboard. For the most part, they receive relatively little attention since they are passive and not very exciting. However, recently many motherboard manufacturers have been skimping on capacitors by either reducing the number on the board, or using smaller or cheaper ones. Over time, cheaper capacitors tend to dry out and lose their effectiveness. The result of this corner-cutting is possibly spurious signals on the board (causing problems that are virtually impossible to troubleshoot) and reduced motherboard life. The only real way to protect against this sort of cheap construction is to avoid buying motherboards only on the basis of price. Look for name brands on the capacitors, and to make sure that they are a good size. Capacitors of the type used on motherboards generally come in two flavors: tantalum or electrolytic.

23. Keyboard and Mouse Connectors The types of keyboard and mouse connectors your PC will have depend on the style and form factor of your motherboard. There are generally two arrangements. Newer PCs, PCs using the ATX, LPX or NLX form factors, and many proprietary (brand name) machines, use a pair of small 6-pin connectors for the keyboard and dedicated (PS/2) mouse. Older PCs using the AT form factor use the older, large, 5-pin keyboard connector, and do not have a dedicated mouse port connector. These PCs use a serial port for the mouse. Some motherboards don't come with a built-in PS/2 mouse port, but include a header for a PS/2 mouse port, which you can use to add a PS/2 mouse port yourself. These connectors are located at the back of the motherboard.

24. Keyboard Controller The keyboard controller does what the name implies. It also controls the built-in PS/2 port, if it exists on the motherboard. On some newer PCs, this controller is in fact further integrated into the Super I/O controller chip, so your motherboard may not have a separate chip for it.

25. Real-Time Clock and CMOS Memory Chip This chip holds the real-time clock that keeps the date and time on your PC, as well as the CMOS RAM that holds your PC's BIOS settings. It is powered by the PC's built in battery, which may in some cases be built into the real-time clock package itself. This chip is often marked "Dallas", after Dallas Semiconductor, the company that makes a large number of them.

26. Super I/O Controller The Super I/O controller chip performs many of the standard input/output functions that used to be done by multiple smaller chips. National Semiconductor makes a large number of these chips, and they can sometimes be identified by looking for this name on the surface of the chip.

27. Battery The PC uses a low-power battery to maintain certain information when the power is off; for example, your BIOS settings, the current date and time, and resource assignment for Plug and Play systems. Some PCs use a battery soldered to the board that looks like a small cylinder or barrel. It is not generally detachable. Some PCs use a flat round watch battery in a metal holder.

28. BIOS Chips The system BIOS is coded into read-only memory (ROM) chips that are placed on your motherboard. There are usually one or two BIOS chips, depending on the board, and often labeled with the name of the BIOS software company (usually Award or AMI) Some PCs don't appear to have a battery at all. In this case, the battery may be a lithium type that is within one of the other packages (typically the real-time clock package). It may also be an integrated rechargeable Nickel-Cadmium battery (sometimes called an "accumulator") that is recharged whenever the line power is connected to the machine. These batteries cannot be replaced, although they are rated for a long life (5 to 10 years). JP1, JP2 etc. For some functions, a group of jumpers is used.

29. Jumpers Jumpers are pins on a motherboard or other device, that are used to provide configuration information to the hardware. A single jumper consists of a pair of pins, with a small rectangular shunt that can be placed over both pins to short them together. The hardware is programmed to act one way when the jumper is shorted, and another way when it is left open. The jumpers are normally numbered One of the newest innovations on the market is the "jumperless" motherboard, such as the IT5H made by Abit. With these boards you make many of the hardware settings, such as CPU type and speed, and even CPU voltage, using BIOS settings, while some others are retained as regular jumpers (typically, CMOS clear and cache size). This arrangement lets you change the clock speed of the CPU as easily as you would change any other BIOS setting, and makes upgrading the processor a snap. It also makes it easier for motherboard manufacturers to add support for new processor types as they are put onto the market. Many people think that "jumperless" is the new wave of motherboard design, and certainly the ability to change more settings without opening up the box is a great advantage. Others like the control of being able to physically set a jumper Every motherboard differs in its jumper numbering, positioning, and most importantly, what the settings for each jumper mean. This is why having the motherboard manual is so crucial for any technician who is troubleshooting a PC. This procedure provides specific instructions and caveats for configuring your motherboard.

30. Ports and Headers Ports are connectors used to connect external cables and devices to the motherboard. In addition to the keyboard and PS/2 mouse connectors, some types of motherboards (such as the ATX) have on the back edge of the motherboard integrated serial and parallel ports. Motherboards that don't use integrated ports, use headers on the motherboard instead. Headers are groups of pins used to connect devices or ports to the motherboard. A cable runs from the port and is plugged into the header on the board. The following are the headers that are commonly found on a typical Baby AT style motherboard (though some of the functions are provided as headers to ATX style boards as well, if an integrated port is not provided): Serial Ports: As mentioned, there are usually two serial port headers. Each has 9 or 10 pins (only the first 9 are used, however). Parallel Port: This header is used for the external parallel port and has 26 pins (25 are actually used). PS/2 Mouse Port: Some good motherboards provide a header for a PS/2 mouse port when this port is not already on the board. This lets you add a PS/2 port yourself. The PS/2 mouse header has 5 pins.

31. Ports and Headers Ctd. USB (Universal Serial Bus): A new technology, USB is proposed to be the new standard for connecting devices such as keyboards, mice and external modems to the PC. Since it is not in common use yet, many motherboards provide a header for you to run a port for it in the future if needed, instead of an actual port (which will appear on future boards if and when USB catches on). This header has 10 pins. IR (Infrared) Port: Some motherboards have a header to allow you to run a connection for an infrared communications port, typically used for wireless communication to printers and similar devices. Infrared ports are far more common on laptop computers than desktop machines. These headers have 4 or 5 pins. Primary and Secondary IDE/ATA Hard Disk Interface: Most newer motherboards have integrated headers for two IDE channels. Each has 40 pins. Floppy Disk Interface: Almost all new motherboards provide a 34-pin header for the floppy disk cable. SCSI: Some motherboards have integrated SCSI ports or headers, though they are uncommon. They are either 50 or 68 pins in size, depending on the flavor of SCSI implemented.

32. Pin Connectors The motherboard provides several connectors that are attached to the case LEDs, indicators, and switches. These (as usual) vary by motherboard, but the ones described here are typical. The physical layout of these connectors can vary a lot as well; some motherboards physically separate these connectors on the board while others group many together into a large "multifunction connector". Functionally there is no difference but it is easier to make an "off by one" connection mistake on a multifunction connector. These are the pin connectors you will typically find on a modern motherboard: Power LED and Keylock Switch: These are two different functions, each requiring two pins, but for historical reasons, they are often combined into a single 5-pin connector. Older cases had the keylock and power LED wires going to a single 5-pin plastic connector. On newer cases they are often separated (in fact many newer cases have no keylock switch) but the 5-pin motherboard connector remains for compatibility. Here is its usual configuration. Note the unused pin between the two power LED pins:

33. Pin Connectors Ctd. Reset Switch: This 2-pin switch has no polarity so you can connect it either way. Turbo Switch: Another relic of the past, many motherboards still include this connector, even though it ceased having any real meaningful purpose after the early part of the 486 generation of motherboards. In most cases it is best just to leave it unconnected. Power Switch: On ATX systems there will be a connector for attaching two leads from the case power on/off button. On ATX PCs the power switch sends a signal to the motherboard to turn on the PC; it doesn't attach directly to the power supply as it does on older AT style systems. Turbo LED: This is the counterpart to the turbo switch of course.

34. Pin Connectors Ctd. IDE/ATA Hard Disk Activity LED: This connector signals the LED when the motherboard detects activity on any of the system's IDE hard disks. Some motherboards have four pins for this connector. On many of these the four pins represent two different pairs, both of which work: pins 1 and 2 are one pair and 3 and 4 are another, and either pair can be used. On other motherboards, only two of the pins can be used; you need to check your motherboard manual. Speaker: This is a 4-pin connector for the case speaker, but only the two outer wires are used. There is no polarity here either, you can connect the speaker either way. CPU Fan: Some motherboards have a 2-pin connector for powering the processor's fan, if the fan has the right type of power connector. Many fans just connect to the regular power connectors from the power supply. Suspend Mode Switch: Some systems have a two-pin connector for a toggle switch to put the system into suspend mode. The turbo switch button on the case can be used for this function on newer systems. Suspend Mode LED: Some systems have a connection for an LED that is lit when the system enters suspend mode, either by using the suspend mode switch or through automatic power management.

35. System Chipset and Controllers The system chipset and controllers are the logic circuits that are the intelligence of the motherboard. They are the "traffic cops" of the computer, controlling data transfers between the processor, cache, system buses, and peripherals-- basically everything inside the computer. Since data flow is such a critical issue in the operation and performance of so many parts of the computer, the chipset is one of the few components that have a truly major impact on your PC's quality, feature set, and speed.

36. System Chipset and Controllers Ctd. What exactly is a "chipset"? A chipset is just a set of chips. At one time, most of the functions of the chipset were performed by multiple, smaller controller chips. There was a separate chip (often more than one) for each function: controlling the cache, performing direct memory access (DMA), handling interrupts, transferring data over the I/O bus, etc. Over time these chips were integrated to form a single set of chips, or chipset, that implements the various control features on the motherboard. This mirrors the evolution of the microprocessor itself: at one time many of the features on a Pentium for example were on separate chips.

37. System Chipset and Controllers Ctd. The system chipset in most cases does not integrate all of the circuitry needed by the motherboard. Most motherboards have the following controllers on them: The system chipset itself. The keyboard controller, which manages not only the keyboard but also the integrated PS/2 mouse The "Super I/O" chip, which handles input and output from the serial ports, parallel port, floppy disks, and in some cases, the IDE hard disks as well Additional built-in controllers that are normally found in expansion cards: video, sound, network and SCSI controllers being the most common.

38. Additional Integrated Motherboard Functions On some motherboards, circuitry is included to perform some of the common functions normally found on expansion cards. This definitely has its pros and cons, depending on what is included, how they do it, and what your needs are. In general, incorporating built-in circuitry has the advantage of lower cost, and the disadvantage of lower choice and upgradability. Integrated Motherboard Video Integrated Sound "Card" Integrated Network Interface Integrated SCSI Controller

39. Integrated Motherboard Video The video card is one of the more important performance- related features on a PC; having it included on the motherboard eliminates the possibility of choosing a card to meet your particular needs. In addition, motherboards with integrated video are notoriously difficult to upgrade. Many that have an option (via jumper or BIOS setting) to disable the on-board video actually still have problems with an add-in upgrade video card, and many come with no ability to disable the built-in video at all! On a lower-end machine however, integrated video can save some cost over buying a separate video card, as well as an expansion slot. These motherboards are often found in the LPX form factor, where saving space and cost is normally a priority.

40. Integrated Sound Card Integrated sound support is fairly common, particularly on retail brand-name machines. Even the lesser clones have figured out by now how to do basic SoundBlaster emulation. However, bear in mind that sound cards use many system resources and can cause many hard-to-diagnose problems when they are of low quality. Most of the integrated devices provide rather basic functionality not approaching the high-end capabilities of the real add-in cards.

41. Integrated Network Interface Integrated network adapters are relatively rare on motherboards though all branded workstations nowadays come with inbuilt 10/100Mbps card. In some ways, this is one of the least offensive of the integrated controllers discussed in this section, provided it emulates a common standard (such as NE2000-compatible 10 /100Mb/second Ethernet), and it comes with good drivers.

42. Integrated SCSI Controller Some motherboards come with built-in motherboard SCSI support. One of the problems with SCSI is the large number of constantly changing standards and protocols.

43. Extras for the motherboard In addition to the motherboard itself, a good quality motherboard should come with the items described in this section:: Motherboard Manual I/O Connectors Floppy Cable IDE/ATA Interface Cable

44. Motherboard Manual General Information: The model number of the board, the name of the manufacturer, and contact information. You need this to get help, BIOS upgrades or information on your board. Assembly Instructions: Instructions on how to install, jumper, and configure the board. Some motherboards put this on a single page; others include a 50-page-plus manual. This should include a diagram of the board showing where all the components are. If this diagram doesn't look like the actual board (it happens!) you could have trouble, but not always. It is also fairly common for there to be slight differences between what is actually on the board and what the manual says. Be very careful to watch for these.

45. Motherboard Manual ctd. Configuration Information: Information on acceptable processor and memory configurations for the board. You need this information to determine what processor and system memory to buy. BIOS Manual: An explanation of the board's BIOS settings, what they mean, and how you should set up the machine. These manuals (which are sometimes separate from the motherboard manual and sometimes just a second section in a single manual) range in size and quality much like the assembly instructions. However, there are many Internet resources to help with BIOS settings. Motherboard assembly instructions are much more board-specific and so are harder to find outside the manual itself.

46. I/O Cables or Connectors If your motherboard uses the ATX, LPX or NLX form factors, it has integrated serial and parallel port connectors. If it is AT or Baby AT style, then you normally should get three ribbon cables with the motherboard to connect the serial and parallel connectors to the motherboard. The serial cables normally have 9 wires each (even if they go to 25-pin connectors) and the parallel cable has 25. These connectors normally come pre-mounted into metal inserts intended to be installed into the case where expansion cards go.

47. Floppy Cable The motherboard should come with one "standard" 34-pin floppy disk cables. This is the unusual-looking cable with 5 connectors on it (one plus two pairs), with a half-twist in 7 of the wires in the middle of the cable.

48. IDE/ATA Interface Cable A motherboard normally comes with one standard 40- pin IDE (ATA) hard disk / CD-ROM cable. It should have 3 connectors on it, but sometimes will only have 2. If you want to use two IDE channels (which is preferred in most cases for performance reasons), you will usually have to use an additional interface cable. A standard, 40-wire IDE/ATA cable. Note the presence of three black connectors, and the 40 individual wires in the ribbon cable. Also note the red wire that marks wire #1 and hence pin #1 on each connector.

49. In conclusion… A good motherboard should be solid and well designed Such boards reduce interference problems because of their design, and reduce the chances of problems in assembling the PC. Cheaper flimsy boards increase chances of a (virtually impossible to diagnose) electrical problem on the board The motherboard also defines the computer type, upgradeability and expansion capability