What’s in the Box – The Motherboard
A computer is a fairly complicated device containing lots of different parts. This month I am going to take a look at one of the parts that you will find inside of your computer case and give you some idea of what its various components do. Armed with this knowledge you will have a better idea of what you are looking at when next you go to buy a computer.
The most complicated part of the computer is the flat circuit board (called the motherboard) into which most of the other devices within the computer are plugged. We’ll start by considering what components are found on the motherboard and what part that they play in the operation of your computer innotechreviews.
There are a number of processing chips that are hard wired onto your motherboard. One of these is the BIOS chip (basic input output system) which contains the permanent memory that contains the instructions that tell your computer how to start up and load the operating system. The information contained within the BIOS chip can be updated to correctly reflect the setup of your computer by running a special program contained within the chip when you first start the computer. This program is accessed by pressing a special key combination (usually just the delete key) just after the computer first starts up. Some motherboards have a second BIOS chip to provide additional protection against the content of the BIOS memory getting corrupted. Most modern BIOS chips also allow you to change the programs stored in the chip by running a special program. This is known as flashing the BIOS.
One chip on the motherboard needs to run constantly even when your computer is off. For this reason this chip is powered by a battery that you will also find on the motherboard. This chip is the RTC chip (real time clock) which keeps track of the current date and time.
The two biggest chips that you will find hard wired to your motherboard are known as the north bridge and south bridge chips. The north bridge chip is responsibe for controlling the central processing unit and all of the random access memory that are plugged into your motherboard. The south bridge chip controls most of the other devices on the motherboard such as the PCI bus which has most of the peripheral devices either built into the board and hence permanently connected or which can be plugged into the various “slots” that can be found along the back edge of the motherboard. Computer motherboard manufacturers have recently been working on redesigning the method that these two chips use to communicate with one another as the increasing speed of the many other components within the system mean that this has rapidly approached the point of becoming the bottleneck in communications within your computer. It is these two chips which between them control the communications between all of the other components in your system.
These days there are usually a number of computer sub-systems built into the motherboard which in the early computers had to be plugged in separately. In the earliest computers even the RTC chip had to be installed via a plug in card. Today the EIDE hard disk controller, the floppy drive controller, serial port controller, parallel port controller, and USB port (universal serial port) controllers are almost always built into the motherboard and run off of the PCI bus that is controlled by the south bridge chip. Some computers even have integrated sound or networking and while this adds to the expense of the motherboard and makes upgrading more difficult this may be the ideal solution for a cheap business system. Other controllers are also occasionally integrated into motherboards eg. SCSI controller.
Also to be found on the motherboard are a number of sockets and slots that allow you to plug other components into the motherboard in order to convert it into a complete computer. Attached to the north bridge are the processor slot or socket where the CPU chip is plugged in as well as the memory sockets where the main memory gets plugged in. The design of these sockets (as well as the programming incorporated into the various chips on the motherboard) will determine the type and speed of the processor and memory that can be used with this motherboard.
Attached to the south bridge are the main slots along the back of the computer where the various other devices get plugged in. In early computers these slots consisted mostly (or entirely) of 8 bit or 16 bit ISA slots with perhaps one slot extended to the VESA standard to take the graphics card. Some 386 computers through early pentium systems also had a 32 bit version of the ISA slot called an EISA slot. More modern computers use PCI slots (mostly the 32 bit variety but a longer 64 bit version also exists). They may also have a single AGP slot that is designed to take the graphics card. Finally there will be a number of sockets on the motherboard providing the means whereby the integrated controllers previously mentioned can communicate with their associated devices.