PREFACE:
Pictured below is an Intel Pentium 5 processor based AT form factor motherboard. Yes this is antiquated but it is very similar to today's motherboards/mainboards. The main difference being that on today's motherboards you will find different expansion slots like AGP, PCI-E and built in sound, RAID, NIC/LAN and Video. The built in components are usually not as good as the expansion cards but can suffice for many applications. Built in LAN/NIC solutions are typically the exception to this rule. Built in sound is usually sufficient for most people and unless you are an audiophile you won't notice the difference. But built in video is typically very limited and insufficient for playing most games.
Click on an item on the picture to link to it's explanation.
Mounting Holes: These holes come in different configurations depending on the motherboard configuration and size. Most computer cases allow for these varied hole configurations. These holes allow you to mount the Motherboard with necessary hardware to the computer case chassis. The hole in the middle on the left side should be mounted with a metallic standoff screwed into the case chassis and a metal screw screwed through the top of the motherboard (as viewed in picture) to the metal standoff that will be below the motherboard as this serves as a ground to the chassis and a rigid mounting point. A fiber washer should be mounted on the screw used to absorb any irregularities between the screw head and the soldered surface around the hole, this helps in not tightening the screw too much. Be careful not to tighten this screw too tightly as you might damage the motherboard (you know you've gone too far when you hear a crunching sound-which means it's time to replace the motherboard!) an eighth of a turn after the screw just meets the motherboard face is enough. An electrical contact will be made between the metal standoff and the solder around the hole on the bottom of the motherboard. All other holes use plastic snap-in standoff's. These stand-off the motherboard from the case chassis which isolates the electrical paths on the bottom of the motherboard from the case chassis. All hardware (screws, fiber washer, and plastic standoffs) usually are supplied with the case.
Power Supply Connector: There are two bundles of cables that each have a flat connector on the end that come from the power supply in the case. Each of these connectors take up half of the motherboard connector. Each of these connectors have fingers on one side that only allow you to place them on this motherboard connector in only one way from top to bottom-fingers facing away from the back of the motherboard power supply connector. These connectors are snapped into place side by side. HOWEVER, you can put these connectors on in the wrong sequence side by side-left to right or right to left. The correct method is so that the black wires on the power supply connectors are next to each other in the middle of the left to right or right to left configuration.
Integrated Multi I/O: These connectors provide (from top left to bottom) two serial (COM) ports, a parallel (printer) port, two IDE (hard drive) ports, and a floppy drive port. The serial ports and the parallel port connectors on the motherboard are connected to their respective connectors via ribbon cables. The IDE and floppy drives are connected with ribbon cables as well. All these cables should be supplied with the motherboard. Lets talk about the parallel cable and connector first. On one end of this cable is the connector that is inserted onto the motherboard and on the other end of the ribbon cable is the connector that is mounted to the case and provides the standard female 25 pin DIN connector that you attach your printer cable to. The motherboard connector on the end of this cable has to be inserted into the motherboard socket such that the red stripe on the ribbon cable matches up with pin 1 of the motherboard socket connector. Pin 1 of the motherboard socket connector will either be marked on the motherboard or shown on a diagram in the motherboard manual. All of these cables have to have the red stripe on the ribbon cable and ribbon cable to motherboard connectors matched up with pin 1 on the motherboard socket connectors. The serial port connectors that are attached to the case come in two configurations, a male 9 pin DIN and a male 25 pin DIN. The 9 pin DIN is the most commonly used for COM port 1 which is the most commonly used for a serial mouse. Serial mice commonly have a female 9 pin DIN connector on them. Since most modems are commonly configured for COM port 2, the second comport on the motherboard may not be used or may be set to COM port 3. In either case, the configuration of these COM ports on the motherboard have to be configured in the BIOS when the computer is booted. Also keep this in mind. COM ports 1 and 3 use the same IRQ(4) and COM ports 2 and 4 use the same IRQ(3). An IRQ is an Interrupt ReQuest. The CPU sends data to devices through an IRQ number and ultimately, the IRQ controller. There are a limited supply of IRQ numbers, 16. These IRQ numbers are used by all hardware devices, video card, sound card, COM ports, Parallel port, Hard Drive controllers (IDE and SCSI), joystick port, keyboard, PS/2 mouse, and more. Most devices do not respond well by sharing the IRQ with another device. So if you are using a modem on COM port 2, I would not use the second COM port that the motherboard provides unless the BIOS allows you to configure the second COM port to an IRQ that is non-standard and is not used by any other devices (very unlikely). If you have a MODEM that can be configured to a different COM port and IRQ and there are enough IRQ's to go around (again very unlikely) then go ahead and use it. If you have an external modem that connects through the second COM port, then all is well, connect this port up and use it. One more note, don't let PLUG AND PLAY fool you, this only allows the PnP device to automatically configure itself to open resources, assuming the drivers the PnP devices provide for WIN95 support it, there is still a limited number of IRQ's. Now we can move on to the IDE connectors, each IDE port (there are two here) support two IDE devices. So a maximum of four IDE devices are supported by this motherboard. Each IDE port is either the primary (logical port 0, IRQ 14, hex address 1f0) or secondary port (logical port 1, IRQ 15, hex address 170). Since these are accepted standards, most BIOS's do not allow these to be changed, only enabled or disabled individually. There are only two IDE devices that I know of, a CD-ROM and a Hard Drive. Each device must be configured as a master, slave, single or cable select (a jumper on the back of the device - read it's manual). If you are putting two IDE devices on one IDE port, either one device is configured as master and the other device is configured as slave or both devices are configured for cable select. Cable select requires a special IDE cable and is very rare. If only one device is attached to an IDE port, then it is configured as single. Remember that the device configured for master on the primary IDE port will be recognized as C: which is the drive the computer boots from. If you have two IDE devices, they do not have to both be on the primary IDE port, your boot drive should be on the primary IDE port and the other device can go on the secondary IDE port. An example is in order. I have 4 IDE devices, 3 hard drives and 1 CD-ROM. I have two hard drives connected on the primary IDE port cable, the boot hard drive is configured as master (C:), the second hard drive is configured as slave (D:). On the secondary IDE port cable, the third Hard drive is configured as master (E:) and the CD-ROM is configured as slave (F:). You could have a boot drive configured as single on the primary IDE port cable (C:) and a CD-ROM configured as single on the secondary IDE port cable (D:). One last note, sound cards today come with an IDE controller on them to connect an IDE CD-ROM and most CD-ROM's bought in kits come with an IDE controller card. If you use either of these, they are typically set to the secondary IDE controller configuration which means you have to disable the secondary IDE port on the motherboard through the BIOS at startup. I have such a sound card but chose not to use the IDE port on the sound card so I disabled the port on the sound card. And one last general note about PnP versus Legacy devices. The BIOS on this motherboard supports PnP, sometimes PnP has to be disabled in the BIOS if you are having trouble with a combination of Legacy and PnP devices so that you can setup all devices manually (either on the legacy cards, in the BIOS, or in WIN95) to work properly under WIN95, the PnP BIOS can be re-enabled after you have got things straightened out. Legacy devices are older devices that use jumpers to configure settings and do not support PnP.
USB stake-pin connector: This connector will attach to the Universal Serial Bus cable, when it is used, it is interesting to note that this motherboard supports USB, although there is no cable for it, and there are no devices that support it yet. However, USB is supposed to be the rage of 97.
PS/2 Mouse stake-pin connector: I love a PS/2 mouse, it uses IRQ12 and frees up COM port 1 so that I can transfer files from my laptop. Again there will be a ribbon cable with a connector at either end. On one end of the cable is the connector that attaches to the stake pins on the motherboard, line up the red stripe with pin 1. The other end of the ribbon cable has a standard female PS/2 connector that mounts to the computer case. A standard PS/2 mouse has the male PS/2 connector on it that you plug into this female connector. Remember to enable PS/2 mouse support by either a jumper on the motherboard or an option in the BIOS (see the manual). A note about the serial, parallel and PS/2 case connectors. These connectors are usually mounted to metal strips that are mounted to the case and block access to either PCI or ISA slots. Some cases today have additional slots in them so that this does not happen. But if yours doesn't, you can dismount these connectors from these metal strips and mount them into knock-out holes in the back of the case. Some serial mice can be connected to a PS/2 port with a connector changer, but not all, best to get a mouse designed for a PS/2 port.
New DIMM Sockets: This is a new memory standard that allows for very large density memory modules, I have not seen any as yet.
72 Pin SIMM Sockets: These sockets are where you mount the 72-pin memory SIMMs. There is a notch on one end of the socket and the SIMM so that they can only go in one way. The clips on the sides of the motherboard SIMM sockets snap the memory SIMMs into place. The SIMMs are inserted by tilting them at a small angle while keeping the bottom gold stripped edge firmly pressed DOWN into the SIMM socket then rotating them to a standing position. On a fresh motherboard, the metal snaps can very tough, use your thumbs to spread these apart a little, four hands is handy! 72 pin SIMM RAM memory comes in three configurations, EDO, parity, and non-parity. This motherboard supports EDO which is much faster than standard parity or non-parity. EDO is EDO, do not worry about parity or non-parity with EDO. Older 72 pin SIMM RAM MEMORY came in two configurations, parity and non-parity, a parity SIMM is defined as Xx36 where a non-parity is defined as Xx32. The X is the amount of 8-bit RAM on the SIMM. So a 4x32 72 pin SIMM provides 16MB of non-parity RAM. Remember that 72 pin SIMMs are installed in 2's, one SIMM by itself won't work, a 4x32 and a 2x32 probably won't work, I wouldn't even try it, nor would I mix EDO with any of the others, nor would I mix parity with non-parity, keep all your memory the same. Not all motherboards support all of these memory configurations. Also read the manual to see which bank gets which SIMMs as they are installed in pairs, a memory bank consists of two SIMMs, there are two banks on this motherboard, the manual will tell you which bank to fill first. You can have 2 16MB EDO SIMMs and 2 32MB EDO SIMMs for example. The 2 16MB EDO SIMMs get put into one bank and the 2 32MB EDO SIMMs get put in the second bank. You can mix between banks, that would be 1 32MB EDO SIMM and 1 16MB EDO SIMM in each bank, this should be avoided. One last note about using EDO memory in a motherboard that does not support it, it may show half the actual memory, work just fine, or not work at all, it may even damage the motherboard or the memory, so don't do it.
Keyboard Connector: This is the standard circular 5 pin DIN keyboard connector, there is a hole in the back of the case that allows you to plug your keyboard directly into this connector that is mounted on the motherboard. Some motherboards use a PS/2 connector instead. There are adapters that will convert from one to the other.
Pipeline Burst Cache Socket: This socket accepts a cache SIMM and can only be inserted one way. Typical configurations are either 256KB or 512KB. Todays motherboards dont have these as the Cache is built into the processor.
CMOS and Clock Battery: This motherboard has a replaceable button battery. This battery is necessary to maintain the clock and BIOS settings when the computer is turned off. Some motherboards do not have a replaceable battery (it is soldered to the motherboard) while others use a BIOS that has the battery built into the BIOS chip. I like this one.
PCI Expansion Card Slots: The PCI architecture is a faster, wider bandwidth interface for expansion cards. An example would be a PCI video card or SCSI or IDE controller. The multi-I/O IDE controller built into this motherboard is connected to the PCI bus without taking up a PCI connector.
ISA Expansion Card Slots: Many expansion cards are still designed for this aging slot architecture, examples include sound cards, Multi-I/O controllers, SCSI controllers, scanner controller cards, modems, etc.
ZIF CPU Socket: The CPU of choice gets inserted here. A small lever on the side of the socket rotates up so that the CPU can be placed into the socket freely (it falls in and only goes one way). Then the lever is rotated back down into position (usually with a scrunching sound) firmly locking the CPU into place. The Zero Insertion Force Socket does not require any pressing force at all. This motherboard supports CPU's ranging from the 75 MHz Pentium to the 200 MHz Pentium or Pentium pro and supports the new MMX Pentium CPU's soon to be available. This motherboard also supports Cyrix and AMD CPU's as well as Intel.
BIOS: The Basic Input Output System is software that is programmed into a chip. This motherboard has an AWARD Flash PnP BIOS. AWARD is the licensee of the BIOS just like AMI, but don't be confused by the brand name, if you call AWARD or AMI for a BIOS upgrade, they will point you to the motherboard manufacturer. AMI does support AMI BIOS's for the motherboards they produce. Flash means the bios can be updated from a file provided by the motherboard manufacturer if he releases one, usually this process requires setting jumpers on the motherboard. PnP means the motherboard and BIOS supports Plug and Play. You can access the BIOS usually by pressing a key (usually the DEL key) when the computer is booted (turned on) just after the memory check is completed. In the BIOS setup is where you can setup the motherboard devices.
Jumper Stake-pins: These pins are configured depending on the voltage requirements of the CPU.
Voltage Regulators: These are mounted to large heat sinks and along with the Jumper Stake-pins are necessary to provide the wide voltage range requirements of the many different CPU's the motherboard supports.
Chipset: The rest of these VLSI chips on the motherboard provide all the necessary links between I/O, CPU and memory. A motherboard's performance can be limited by a poor chipset. An interesting note is that some motherboards have sound cards integrated right onto the motherboard, this is the Prego concept - IT'S IN THERE!
The motherboard selected has to support the selected CPU by manufacturer as well as model and internal clock speed measured in MHz or MegaHertz. Pins on the bottom of the chip fit into the CPU socket on the motherboard only one way. The CPU also requires a combination heat-sink and fan. The heat-sink and fan connect into a power connector, sometimes provided on the motherboard next to the CPU socket, if it isn't, then a power splitter will also be needed.
