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Main Computer Components
As reading on it's own can be hard on the head I have included a few links to photo's and illustrations that might help you get the concept of what I'm talking about.
Here is a short tutorial with pictures on the inside workings of a desktop computer. Could be useful to check it out before you read on. Click here.Here we also have Pictures of various components that make up the typical PC
CaseCases come in many shapes and sizes and are often chosen by how they look. Personally I'm not too bothered how they look as long as they do the job. But as with many things they can become a focus and these days many people customise their cases with fancy lights and see through panels etc.
There are two main shapes. One is the Desktop case, which lies flat on the desk normally with the monitor sitting on top and the other is theTower case, where everything is stacked one above the other. There are various sizes of tower and the difference is how many available bays there are for things like cd-rom, cd-writers and other devices one might want.
The bigger the case the more space inside to work with and the easier to build, the only drawback here is with the full-tower case, where the length of the cables needed inside are not standard size and therefore add to the cost. A midi tower case is probably the best option with either three or four 5.25" bays.
There are cases made by various manufacturers such as IBM, DELL etc which are not standard and will only take the mainboard etc they were made for. They are not such a good bet for upgrading as they don't take the standard components and if you need spares such as power supplies then they can be expensive.
The next factor involved in choice of case is the physical layout of the back. There are two types of standard case. One is AT and the other is ATX. It is important to have the correct one for the Main Board being used as they are not normally interchangeable, although some cases can be adapted to take either type.
With an AT case, the sockets you see visible at the back of the computer are connected to the motherboard with cables inside the case, which sometimes leads to very cluttered inside. These are for the Mouse, Printer etc. At time of writing (Feb 2004) AT cases are not normally available anymore, and are not worth upgrading. With an ATX one, these sockets are part of the motherboard. This results in a much less cluttered system inside and although slightly dearer, a much easier system to build. These days the ATX has become the most used and is now a standard.
The power supplies in the two types of cases have different plugs on the end of the cables that go to the motherboard. Some mainboards have both types of socket so it can be used in either type of case. Certain modern cpu/processors need a higher rated power supply of 400 Watts or more and the standard 300 Watt will give problems. It is something to watch for when building a new, faster system.
MainboardThe basis of the computer system is called the Mainboard also known as the Motherboard, presumably because everything else fits around it. This is now often shortened to Mobo.This is the large board in the computer that everything plugs into. The motherboard basically controls all the functions of the computer and is the link between all the other parts.
This is the bit that limits the function of everything else and by that I mean, it decides the maximum speeds etc. Data is shifted around the motherboard on lines called "buses". There are different types of "bus" The frequency of the "bus" these days is 66Mhz for older systems. Later ones run at 100Mhz (Megahertz) and 133 Mhz, 266Mhz and more recently 400Mhz. The abbreviation for this is FSB (front side bus).
You will find that the lower cost motherboards will sometimes have other components built in, such as Video card, Sound card, Modem and Network card, which is great for a basic starter system and brings the price down. Very good for building a cheap workable system but beware when comparing system prices as a more expensive system will have more flexibility because it has seperate components which can be upgraded easily. The all in one boards usually have less slots for extra cards.
CPUThe next part we can look at is the Central Processor Unit or (CPU)
as its known. This is basically the brain of the system and is the part that does all the calculations and runs the programs by carrying out a sequence of steps one at a time at very high speed. To give you an idea of the speed, a processor running at 500 Megahertz is doing 500 million steps a second. This speed would be obtained by multiplying the "bus" speed by a factor of five ie 100Mhz X 5=500Mhz.
Everything the computer does is based on something called binary code and that uses two digits, 0 and 1 as opposed to decimal which uses 0 to 9. In decimal as you know we have the units, tens hundreds etc. In binary the columns go 1-2-4-8-16 etc. The number 5 would be represented as 101. "Zero" and "one" is the same as "off" and "on" in an electronic circuit so it can be used to calculate. One of those digits is called a "bit".(short for binary digit)
The CPU is very good at doing what it does, which is shift numbers around by adding, subtracting multiplying and dividing. It only deals in numbers so everything you type in has to be represented by a number and this is done by using one type of code or other.
When eight "bits" or 0's and 1's are put together this is called a Byte and they are used to represent characters in whatever code is being used. There are many different types of code used in computers.
A common one for characters is ASCII. (American Standard Code for Information Interchange)
Main MemoryThe next thing we need to look at is the Main Memory or "RAM" (Random Access Memory) as it's usually referred to. This is where the data is stored, that the processor needs, to run through a program or set of instructions which make up a program.
There are different types and sizes of memory. In older systems, memory had to be installed in pairs and they were called SIMMS (Single Inline Memory Modules) but these days all new computers will accept DIMMs (Dual Inline Memory Modules) which are longer pysically but you only need one. DIMMs run at "bus" speed and and are marked accordingly. PC100 runs at you guessed it 100Mhz and PC133 at 133Mhz. Nowadays we also have DDR Ram which is twice as fast as it runs at double the "bus" speed. There is also one called Rambus which is becoming more common as the price is falling it runs at processor speed which can make it very fast. Rambus was used on the original Pentium 4 Systems.
The size of the RAM is measured in Megabytes (millions of bytes).
Systems these days normally have RAM in the region of 128Mb-512Mb installed. Generally speaking the more the merrier. Investing in more RAM is one of the best upgrades you can do to speed up a system. The basic problem with this type of memory is that when the power is switched off any data held in it is lost. If a system doesn't have enough RAM then the data it is working with has to be shuffled back and forth to the Hard Drive which ultimately slows up the system. Check out the price of our new RAM for a cost effective upgrade if you are in the UK otherwise use the system RAM identifier at the very top of the page.
Hard DriveThis brings us neatly to a system of storage that can hold the data with no power connected and this is called the "Hard Drive" or "hard disc". This device is one that spins a metal disc at high speed and data is recorded onto it in a similar way that data is recorded on a video or cassette tape except that the recording head moves across the surface in a similar fashion to an old record player. The head doesn't actually touch the surface but flies over it very close. These days the storage capacity is between 40Gb (1Gigabyte=1000Megabyte) and 180Gb.
The hard drive has a far greater capacity for holding data than the Main Memory has and can hold all the programs ready for use. When they are required, they are loaded in to memory, by another type of program which is called an "Operating System", the most common of those is one called "Windows" which you are likely to have heard of.
Video CardThe other main component, without which, not much happens, is the "Video Adaptor" or Graphics Card as it's commonly known. This basically translates the output from the computer itself and displays it on a monitor screen.
In cheaper motherboards the video adapter is often onboard. All this means is instead of a seperate board plugging into the motherboard it is already built in as part of the motherboard. Video cards also have "RAM" on them and the cheaper cards have 8Mb (Megabytes) and the more expensive ones 64Mb to 256Mb. In this case more is definitely better.