computer hardware: MOTHERBOARD

What is a Motherboard?

Motherboard is the most important component in any personal computer. It contains almost every important elements of the computer. Sometimes instead of the calling it “motherboard”, IBM refers to is as “system Board” or “ Planner Board” , some other manufacturer refer to this as the “Logic Board”.

The motherboard is the main circuit board inside the PC which holds the processor, memory and expansion slots and connects directly or indirectly to every part of the PC. It’s made up of a chipset(known as the “glue logic”), some code in ROM and the various interconnections or buses.

The original PC had a minimum of integrated devices, just ports for a keyboard and a cassette deck (for storage). Everything else, including a display adapter and floppy or hard disk controllers, were add-in components, connected via expansion slots.

Over time, more devices have been integrated into the motherboard. It’s a slow trend though, as I/O ports and disk controllers were often mounted on expansion cards as recently as 1995. Other components - typically graphics, networking, SCSI and sound - usually remain separate. Many manufacturers have experimented with different levels of integration, building in some or even all of these components. However, there are drawbacks. It’s harder to upgrade the specification if integrated components can’t be removed, and highly integrated motherboards often require non-standard cases. Furthermore, replacing a single faulty component may mean buying an entire new motherboard. Consequently, those parts of the system whose specification changes fastest -

RAM, CPU and graphics - tend to remain in sockets or slots for easy replacement. Similarly, parts that not all users need, such as networking or SCSI, are usually left out of the base specification to keep costs down. The basic changes in motherboard form factors over the years are covered later in this section - the diagrams below provide a detailed look at the various components on two motherboards. The first a Baby AT design, sporting the ubiquitous

Socket 7 processor connector, circa 1995. The second is an ATX design, with a Pentium II Slot 1 type processor connector, typical of motherboards on the market in late 1998.

A conventional motherboard comprises of various components such as:

1) Card slots

2) Power connectors

3) IDE connectors

4) SATA connectors

5) Socket

6) CMOS

7) BIOS

8) Coprocessor

9) RAM slots

Card slots:

These are also called expansion slots. The expansion slots are long thin connectors on the motherboard, near the backside of the computer. Various expansion cards are connected to the motherboards through data, address and control lines/buses on these slots.

One can connect various expansion cards such as display card, hard drive controller, sound card, network card, modem card etc. on these slots. When an adapter card is connected to the expansion slot, it is actually connected to the data, address and control bus on the motherboard.

These card slots are of different types based on their speeds. They are:

1) 8 bit

2) 16 bit

3) 32 bits

4) 64 bits

you might be wondering what exactly does this bits thing mean. It is explained below. A bus is an electronic path on which signals are sent from one part of the computer to another.

These buses are categorizes according to the number of BINARY DIGITS (bits) that they can transfer at a time.

If the data bus is 8 bit wide then it can transfer 8 bits of information at a time and called an 8 bit bus.

On a 8 bit data bus transferring 16 bit data requires two data transfers Another very common term while talking about bus is , its “ bandwidth”. The bandwidth of a bus is the measure of data that can fit in the bus at a given time.

You can increase the data movement through a bus either by increasing the bus width( from 8 bit to 16 bit) of by increasing the bus bandwidth (8 Mhz to 20 Mhz).

This is similar to the way you can increase water output from a pipe, either you can increase the pipe diameter or you can increase the water flow.

Data Bus : Is a set of wires or tracks on the motherboard. Data bus is used to transfer data from one part of the computer to another part.

Address Bus : is a set of wires or tracks on the motherboard Printed Circuit Board(PCB) which is used to specify address of a memory location

Depending on the width and the technology, the expansion slot bus can be

divided into the categories mentioned above.

32-bit card slots

The big long slots are the 8-bit card slots

These are the 16 bit card slots

Power connector:

The motherboard requires electrical energy to pass signals across the bus line to different parts of motherboard. The power comes from the SMPS after filtering the 230 volts of power supply. There are two types of power supplies they are AT and ATX.

AT power supply:

This AT is called Advanced Technology. This gives 12 pins to supply electricity to the mother board. This is used in the old motherboards like in p1, p2, p3 motherboards

ATX power supply:

This ATX is called advanced technology extended. These power connectors are in three different levels. The first level have 20 pins and are found in latest generation of p3 motherboards and first generation of p4 motherboards. The second level have 24 pins and is found in p4 motherboards. The third level consists of 28 pins and this is present in second and third generations of p4 motherboards.

This is the 20 pins power connector

This is the 24 pins power connector

The above marked connectors are the 28 pin power connectors

IDE connectors:

These are the ports where we connect the IDE hard disk drives and floppy disk drives to the motherboards. In the p1, p2, p3 and the beginning of p4 motherboards we have 2 IDE connectors but as there is development in technology and SATA connectors are introduced the function of IDE hard disk has been reduced and motherboards are manufactured with only one IDE connectors and more SATA connectors and floppy drive connectors are being ignored completely.

SATA connectors:

These are the latest technology connectors introduced after the IDE connecters replacing them in these connectors we do not need a jumper section as we can connect only one hard disk to a connector at a time.

Socket:

This is the place where we add processor in the motherboard. A CPU socket or CPU slot is a mechanical component that provides mechanical and electrical connections between a microprocessor and a printed circuit board (PCB). This allows the CPU to be replaced without soldering.To learn more about socket please refer processor.

This is the new socket which is in use now a days

This is the old socket and this is not in use nowadays

CMOS:

This is complementary metal oxide semiconductor. In old IBM XT or compatible system, BIOS, with the help of jumpers, detected what all components are connected to the computer system.

IBM AT and higher systems do not contain these jumper switches and instead use a CMOS memory to store the system configuration, date, and time etc. information. This CMOS memory receives power from a battery accompanying it, this battery helps it retains the information stored in it even when the system is switched off. When an AT or higher system is switched on, BIOS matches the information stored inside the CMOS with the components connected to the system and if it finds some mismatch or error, the BIOS displays some error message, explaining the problem.

BIOS:

BIOS is an abbreviation if Basic Input Output System. It is one of the most important program stored in the ROM. BIOS program lets your application program and the hardware such as floppy disk, hard disk, video adapter etc. communicate with each other. It is pronounced “bye-os”. The BIOS also contains a program called Power-On-Self-Test or POST. This post program checks the motherboard and other devices connected to the computer during the system power-on time. IBM made the original BIOS for their copyright product, but many compatible BIOS program BIOS program are available from Award, Phoenix, American Megatrends Inc. (AMI) etc. various manufacturers.

Coprocessor:

Coprocessor is a special purpose microprocessor, which is used to speed up main processor job by taking over some of the main processors work. Most common type of coprocessor is a math coprocessor. Coprocessor chips are used to help the main processor in carrying out its

various functions.

A math coprocessor helps main processor in performing mathematical calculations Older system (XT, AT, AT-386) required a coprocessor chips to be inserted into special socket on the motherboard, but the current federation of CPU’s have math coprocessor built inside the main processor itself.

RAM slots:

This is the place where we add RAM in the motherboard. Depending upon the type of RAM the RAM slots keep changing. To find which ram is used in a particular generation please go to the page related to RAM.

There are 4 types of RAMs and their slots:

The images are given below: