There are three common interfaces for CPU's today: Socket 7, Slot 1, and PPGA 370. Socket 7 and PPGA 370 look very similar, only differing by number of pins and various voltages. Chips such as the Pentiums, K6's, 6x86's use the Socket 7. PPGA 370, as I said, looks similar but is only used by Intel Celerons and the Cyrix Joshua chips, since they have a license to use the design by Intel. Slot 1 is used for all Intel Pentium II's, III's, and certain Celerons. A fourth which is being seen more often now is the Slot A. Designed to support the AMD Athlon processor, Slot A looks like Slot 1, but is electrically different. Intel would not license their design to AMD. Therefore, depending on the processor you will be using, the CPU installation will be different. Therefore, this step will be divided into two sections. 

Socket 7 

Almost all Socket 7 and PPGA 370 systems make use of the zero-insertion force (ZIF) socket. Therefore, this procedure is relevant with that setup. 

To install a Socket 7 or PPGA 370 Celeron chip, follow this procedure: 

1.) Check the pins. Turn the chip over and inspect the pins. Are they bent? They should all stick straight up. If many of them are bent, then it is best to request a replacement processor. If only a couple are bent and the bend is not that much, then you may be able to use a screwdriver to gently bend the pins back into place. Do so VERY carefully. 

2.) Open ZIF Socket. This is done by grabbing the lever on one side of the socket and opening it. Pull the lever from the closed, level position, to the open, vertical position. You may need to pull the lever out a bit before it will open. Do this slowly and don't force it. You don't want to break the socket. On the way up, you may experience a little more force. This is normal. The top part of the ZIF socket will slide over a bit. 

3.) Orient The Chip. This involves locating Pin 1 on both the chip and the socket. This is easy to do. The chip is always marked at Pin 1. The mark may be a little dot on one corner, a slightly notched corner, or a mark at one of the pins under the chip. On the socket, there is usually a notch on one corner, or a big "1". These corners will be matched up for correct installation. 

4.) Insert Processor. Bearing in mind the orientation determined in Step 3, insert the chip into the socket. With a ZIF socket, the chip should install very easily. It should almost fall into the socket with all pins lining up. That's why they call it the Zero Insertion Force socket. If not, the socket is probably not open all the way. If you do not have a ZIF socket (God forbid!), you need to exercise extreme care. Lay the chip on the socket. Make sure all pins line up. Then, slowly push the chip into the socket. Use your thumb and push on one side of the chip until it starts to go in. Then proceed to another side and repeat. Do this around the chip several times until it is completely installed. 

5.) When done, there should be basically no gap between the bottom of the processor and the socket. 

6.) Close ZIF Socket. Just close the lever. You will probably feel some resistance. This is normal and it should close anyway. If you really need to lean on it, though, check to be sure the chip is installed correctly. When down, make sure the lever snaps into place. You're done. 

Slot 1 

As said before, only Pentium II's, III's, and some Celeron processors use Slot 1. The slot is basically like a long PCI slot, although it is not white. It runs parallel to the SDRAM slots. On each of the four corners of the slot will be a receptor for a screw. Now that we have it spotted, let's install the chip.

1.) Install the Pentium II Rack. Basically, this rack serves as a guide-rail and support for the CPU to rest in. Since the Pentium II processor sticks up high off the board and is rather slim, it would simply be too loose in the slot without the rails. The rails usually come with the motherboard. They will be about the height of the processor and have two built-in screws on one end. Position a rail on each end of the Slot. Use a screw to tighten it into place onto the motherboard receptors. Do this for each side of the Slot. When done, you should have one rail on each end of the slot. Some boards already have them installed so that all you have to do is "unfold" them for use. This is really convenient. 

2.) Install the Cooler onto the Processor. It is much easier to do this, usually, before you push the chip into its slot. All coolers are a little different in the way they attach to the CPU, but most use the little holes on the metal side of the processor to lock into place. With some coolers, you will need to use a support to keep it off the motherboard. This support comes with the rack setup, and you only use it when needed. 

3.) Insert the Processor. It is time to insert the processor into the Slot. The processor has one card-like edge at the bottom of the black cartridge. This edge is keyed so that it can only insert into the slot the correct way. So, push the processor into the guide rails and down all the way to the surface of the slot. Make sure the cooler(or fan) is facing the side near the motherboard's chipset. When you get to the bottom, you will feel some resistance. This is normal. Work the processor in until the little levers at the top of the guide rails click into place, locking the chip in. 

4.) You're done. Wasn't too hard, was it?