At the low end of the processor hierarchy lie Intel's Celeron and AMD's Duron processors. Both are inexpensive and competent for home use such as word processing or surfing the Internet. In the midrange are Intel's Pentium 4 and AMD's Athlon XP processors, suitable for ordinary business use such as spreadsheet calculations or database access. At the high end are Intel's fastest Pentium 4 processors (with Hyper-Threading technology, referred to as HT technology) and AMD's Athlon 64 (a 64-bit processor line), suitable for high-end graphics such as animation, computer-aided design, and the latest video games.

Despite the confusing variety of processors available, today's models all tend to look the same: a square chunk of metal with tiny pins protruding from one side that you drop into a socket on the motherboard. The problem is that not all processors fit into the same sockets; each processor type has a unique size, which means different processors also have different pin counts. Trying to shove a Pentium 4 processor into a socket designed for an Athlon 64 processor not only won't work but will likely damage the processor. So after you decide on the type of processor you want, the next step is finding a motherboard that contains the proper socket for your particular processor. See the "Choose The Right Processor For The Socket" sidebar for more information.

When purchasing a processor, you often have a choice between the retail version or the OEM (Original Equipment Manufacturer) version. Although the processors in both versions are identical, the retail version includes fancy packaging along with clearer instructions for installing the processor and sometimes a heatsink and fan. The OEM version is almost always cheaper than the retail version, but it comes in a plain (usually white) box with minimal instructions.

If you only plan to install a single processor, pick the retail version. You may pay slightly more, but the added instructions are almost always worth the extra expense. The OEM version is intended for sale to computer dealers who install processors on a regular basis and thus have no need for instructions printed on glossy paper with colorful diagrams since they (presumably) already know what they're doing.

Cooling Your Processor

Once you've chosen a processor and a motherboard that contains the correct socket for your processor, the final step is buying a processor-cooling fan. Cooling your processor is an absolute must, whether you opt for a CPU fan or a liquid-cooled unit. If you don't keep your processor cool, expect it to last a few minutes before burning itself out and turning a high-powered processor into a toasted chunk of useless silicon.

Although most people use a typical cooling fan, which clamps on top of the processor and blows hot air away from the processor surface, hardcore users often prefer using liquid cooling units, especially for the top-of-the-line Pentium 4 or Athlon 64FX processors that generate more heat than ordinary processors. Like cooling fans, liquid cooling units clamp on top of the processor, but instead of blowing hot air away from the processor, the liquid cooling unit circulates water or other liquids to carry away the heat from the top of the processor, in much the same way that your radiator cools the engine in your car.

Finding The Right Power Supply

If you're building a system, after choosing the processor, a cooling unit, and the proper motherboard for your processor, you also need to consider the power supply. The most common power supply is known as an ATX, although there are also Mini-ATX, MicroATX, and Flex ATX power supplies. The type of computer case you buy can determine whether you can use an ATX, MicroATX, or Flex ATX power supply.

To provide maximum cooling for your processor, look at the location of the air vents of your power supply. The better power supplies have air vents located on the bottom, which places the air vents near the processor. This allows the power supply air vents to suck away the hot air generated by the processor and provide additional cooling capabilities. Cheaper power supplies have air vents located just in the front, which places the air vents away from the processor and does not help cool the processor. 

Putting It All Together

With your processor, motherboard, computer case, and power supply together, you're ready to start putting your computer together. When building a computer, you need the following:

• A clean, well-lit, flat surface to lay out all of your computer parts.
• A Phillips and flathead screwdriver for opening your computer case and attaching your motherboard inside the computer case.
• An antistatic wristband to ground yourself so static electricity doesn't fry your processor or motherboard when you touch them.
• Plenty of time. Don't rush yourself or you're likely to lose parts or cause an accident such as bending or breaking pins on your processor.

After you have all of the above items in place, it's time to install your processor on your motherboard. Some older processors, such as the original Athlon processors, were slot-based, which meant that the processors looked like thicker versions of expansion cards that slid into a slot on the motherboard. Newer processors, such as the Pentium 4 and recent Athlon versions, are socket-based, which means the processors look like squares with pins protruding from their bottom.

The latest processors fit into ZIF (Zero Insertion Force) sockets, which means they require little force to install or remove. You just drop the processor into the ZIF socket and pull a lever to lock it in place. To remove the processor, you just open the locking lever and lift the processor out. In comparison, older processors used to plug into LIF (Low Insertion Force) sockets, which required you to press the processor firmly in place and then use a special tool that looked like a miniature crowbar, called a chip puller, to pry the chip out. Needless to say, LIF sockets resulted in plenty of bent and broken processor pins and are rarely found anymore except in ancient computers.

Since the newer processors are socket-based, the following steps explain how to install a socket-based Athlon 64 processor. Although the specific details may differ when installing a Pentium 4 processor, the general steps should be similar.

Step #1: Install the backplate. The retention frame and backplate attach to opposite sides of the motherboard. The backplate sticks to the bottom of the motherboard and provides holes for tightening the retention frame in place.

1. Position the backplate on the underside of the motherboard so that the backplate holes align with the holes on the motherboard. When you're satisfied that you know how to position the backplate correctly, peel the liner off the backplate to expose the sticky surface underneath and place the backplate, sticky side up, on a flat surface. (Caution: Avoid touching the sticky surface or else the adhesive may not be strong enough to hold the backplate in place.)

2. Align the motherboard over the holes on the backplate. When the holes are aligned, press the motherboard firmly in place on top of the backplate. The backplate should be stuck to the underside of the motherboard.

Step #2: Install the retention frame. The retention frame wraps around the processor socket and provides a base for holding the cooling fan over the processor. The retention frame attaches to the bottom of the motherboard and uses screws to hold the retention frame to the backplate on the opposite side of the motherboard.

3. Place the retention frame around the processor socket and align it with the holes in the motherboard. Screw it in place to tighten the retention frame to the motherboard. (The retention frame is symmetrical so as long as you align the screw holes of the retention frame with the screw holes in the motherboard, the retention frame will be positioned correctly around the processor socket.)

Step #3: Install the CPU. One corner of the processor socket appears cut off at an angle. This is designed to only allow the processor to fit in one way into the socket. Once you correctly align the processor in its socket, you need to lock down the processor socket lever to clamp the processor firmly in place.

4. Raise the processor socket lever.

5. Align the CPU over the processor socket so that the triangle of the processor aligns with the triangle marked on the processor socket.

6. Drop the CPU into the processor socket. (Caution: Do not force the CPU into the processor socket or you may bend or break pins.)

7. Lower and lock the socket lever. Lowering the lever may take some force. You may want to record the CPU serial number off the top of the processor at this time before you cover it up with the cooling fan. (Caution: Do not apply power yet. Without a heatsink and fan, the CPU will overheat quickly.)

Step #4: Install the CPU cooling fan. The retail version of the Athlon 64 processor includes a heatsink/cooling fan that attaches to the top of the processor in two ways: First, the heatsink/cooling fan unit uses clips to clamp onto the retention frame. Second, the heatsink/cooling fan includes glue that helps it stick to the top of the processor.

8. Remove the clear plastic protective cover that protects the bottom of the thermal heatsink to reveal the adhesive that helps hold the cooling fan in place on top of the processor. (Caution: Make sure the top of the CPU is clean and make sure no dirt, pet hair, etc. gets trapped on the sticky surface of the heatsink/fan.)

9. Align the heatsink/cooling fan over the CPU. (Caution: Make sure the two retention clips on the heatsink/cooling fan align with the two clip holders on the retention frame.)

10. Hook both metal clips under retention frame clips. (NOTE: You may need to use force to attach the second clip in place.)

11. Pull the cam lever and lock in place.

12.Connect the fan plug to the motherboard fan socket.

Installing a CPU is fairly straightforward once you get past the confusing multitude of choices between processors, motherboards, power supplies, and computer cases. To simplify the entire process, many dealers sell complete kits that include the proper computer case, power supply, motherboard, and CPU-all you have to do is add a hard drive, CD/DVD drives, video graphics card, keyboard and mouse, monitor, and an operating system. If you just want to upgrade an older computer, you can also buy CPU/ motherboard combinations so you don't have to worry about buying the right processor with the right motherboard.

Whether you opt for a complete computer kit, a CPU/motherboard combination, or separate parts purchased individually, you'll find that installing a CPU is simple enough for anyone to do. The hardest part is simply deciding what parts you need beforehand.