The motherboard is the main part of your computer that everything else plugs into. Sometimes it is called the system board. A typical motherboard is a sheet of olive green or brown fiberglass with many gold lines on it and chips sticking from it.
By itself, the motherboard is just an empty plate. The stuff that sits on it does the work. On it, we have the CPU, SIMM sockets, BIOS, and slots. On some older boards, there is also a separate math-coprocessor. The gold lines act like roadways of information between all of the components. These roads enable the parts to communicate and perform the functions of your computer.
CPU
The CPU is usually the most prominent chip on your motherboard. It will be imprinted with the type of CPU that it is, such as “486” or “Pentium”, and it will have the chip manufacturer’s logo on it. If you cannot see this, you’ll probably see a CPU fan. This fan is screwed on right on top of the CPU. Its job is to keep the CPU cool while it is on. Today’s CPUs get very HOT while turned on.
The CPU is the computer’s brain. Its job is to process information and sling it around to all of the various parts. CPUs vary in sizes and speeds. They are often very expensive. A slow 486 chip can cost under $50 US while today’s fastest Pentium II’s can go for over $1000 US!
Naming these Things!
Everyone has heard the various CPU names: 286, 386, 486, Pentium, Pentium Pro, Pentium with MMX Technology, Pentium II, 6×86, K6, and the list goes on. The Pentium II is today’s powerhouse CPU. It is sometimes called the 686. CPUs actually get two numbers that classify them. One is the type (486, Pentium, etc.) and the other is the megahertz rating. The megahertz rating measures clock speed, or how fast the processor can sling information around. Although both numbers are important in knowing what kind of CPU you have, the first is much more important. For example, a Pentium-75 is roughly the same speed as a 486-133.
To make things even more complicated, CPUs also get letters attached to their names. Typically, the letters are either “SX” or “DX”. On a 486, “SX” means that it doesn’t come with a math coprocessor. So, a 486SX is slower and cheaper than a 486DX. On 386 chips, SX means that the chip has a 16-bit data bus and no math coprocessor, while the 386DX is a true 32-bit processor with a coprocessor. Today’s modern CPUss typically come with a math-coprocessor embedded into the CPU itself, so SX and DX are not normally used.
Some CPUs are known as clock-doubling or overdrive chips. These chips speed up your system by helping the CPU along. Some actually replace the older CPU while others plug into another slot on the motherboard. When you see computers that end in “DX2” or “DX4”, they have an overdrive processor attached. A 486DX2 means that it is two times faster than a standard 486-33 and runs at 66 megahertz.
Tech Stuff
As talked about above, CPU speed is measured in megahertz (MHz). This measurement is taken in cycles per second. Why does this matter? Well, a CPU measured to be 33 MHz is completing 33 million cycles per second. At 5 cycles per instruction, you can see how this dictates the speed of calculation.
CPUs are described as having certain data paths. This refers to how many bits of information can travel in parallel at one time. For example, a 16-bit data path is a 16 wire path on which 16 bits of information can travel at any time. This results in roughly 2 bytes of information processed at a time. Therefore, such a CPU is said to be a 16-bit CPU. Today’s CPU’s can handle much more traffic. We have 32-bit and 64-bit processors, although only a few expansion cards can take advantage of this.
The address bus is different than the above data bus. The address bus is the wire path that carries addressing information that says where in the computer’s memory to look for certain data. Each wire carries one bit of information. Since computers think in binary (a number system based on 0’s and 1’s), a 2-bit address bus would provide four addresses (00, 01, 10, 11). A 3-bit bus would provide 8 addresses, and so on. The point of all this is that the address bus built into the CPU dictates how much memory the computer can have. A 286 has a 24-bit address bus, thus providing 16,777,216 addresses. This means the 286 CPU can only address 16 MB of memory. The 386 and 486 both have 32-bit address buses which provide 4,294,967,296 addresses. These processors can address 4,096 MB of memory, even though no motherboards have enough slots to hold this much memory.
BIOS
The BIOS is another very important part of your computer that makes its home on the motherboard. “BIOS” stands for Basic Input/Output System, and usually resides on a series of chips. These chips are typically the biggest chips on your motherboard other than the CPU and math-coprocessor. There is usually a big sticker on it that says BIOS. The sticker also says what kind of BIOS it is and what year the BIOS was published.
If the CPU is the brain, the BIOS is the nervous system. It takes care of the behind-the-scenes action, much like our nervous system ensures that we breathe while we aren’t thinking about it. BIOS handles the dirty work. It also kicks in when you turn on your computer, letting the computer know how many drives are present and where they are.
When you turn on your computer, the BIOS determines what hardware is installed. It finds out if the hardware is working and if any of the parts have their own BIOS. If it finds any BIOS type programming on any of the parts, it lets those parts take inventory before returning to its task. For example, most video cards have their own BIOS chip. So, the main BIOS turns control over to the video card until it is done, then resumes to check the rest of the computer.
All of this happens behind the scenes every time you boot. You may notice the POST, or Power On Self Test. When your BIOS tests the hard drive, floppy drive, and keyboard, you’ll see lights flash on them. Once all of this is done, your BIOS loads the operating system. It does this by looking for and reading your various boot up files, such as Config.sys and Autoexec.bat. From there, your operating system takes over.
As you can see, BIOS is important; every computer needs it. And like CPU’s, it comes in versions. BIOS versions are based on years. You can usually see what date your BIOS is by looking at the sticker on the chip itself, but if you don’t have a sticker, you can go to the BIOS screen on your monitor. This is done by hitting F1 shortly after you power up your computer. Here, it should tell you who made your BIOS and when.
Math Co-Processors
Math co-processors are basically number crunchers and very fast calculators. They crank out fast answers to math problems, helping the CPU do its job faster. They take care of the floating point calculations.
Coprocessors are optional in computers; they just speed up math. Do you need one? Well, if you are running math-intensive software, such as CAD drawing or other software that uses arrays, irrational numbers, or trigonometric functions, a coprocessor might be something worth having. Some people think that spreadsheets could use a coprocessor, but really, these do not require much math since the functions are mainly addition and subtraction. For almost all typical business applications, like the word processor, math co-processors are not needed.
If you have a 486DX, Pentium, or later, you already have a coprocessor. They’re built right in. If you have an SX machine, you don’t have one. With these CPUs, you will have to get an external one that fits into a separate slot on the motherboard. If you have such a setup, you’ll find that the coprocessor is almost as large as the CPU. It is probably the most noticeable chip on the board other than the CPU.
Integrated Circuitry
Many times you’ll have your I/O and video circuitry built right on to your motherboard.
Usually, I/O adapters on the motherboard are of the IDE/EIDE interface, and they are marked HDD for hard drive and FDD for floppy. You simply plug your data ribbons into these and you can bypass the need for a separate I/O card. The downside is that if you want to use a system other than that on the motherboard, you have to disable the circuitry on the board. For example, if you want to use SCSI, you’ll have to disable the IDE on the board. For most users, using the IDE interface on the board works just fine.
Other motherboards have built-in video circuitry. This is less common than the drive interface. This allows you to bypass buying a separate video card and it also saves a slot. But, again, if you want to upgrade your video later on, you’ll have to disable the video on the board and buy the new card anyway.
The Rest
The system battery is very noticeable. It is a small cylinder, just like your run of the mill Energizer or Duracell, but shorter. Its job is mainly to keep the system time and a few other settings when the computer’s power is off. If you are asked the time or what kind of hard drive you have when you turn on your computer, you probably need a new battery. Instructions for changing your battery are included with Installing your Motherboard.
The keyboard connector is self-explanatory. You plug your keyboard into it; the prongs on your keyboard wire’s end will match up with the small holes on the connector on the motherboard. This setup is usually located next to the battery.