5.6. Replacing the Processor
The exact steps required to replace a processor depend on many factors, including the type of processor, CPU cooler, motherboard, and case you are using. In the following sections, we illustrate the procedure for replacing a Socket 478 processor. Most other processors, including Socket 462 (A), Socket 754, and Socket 939 models, require similar steps. Socket 775 processors differ significantly, so we illustrate the installation of a Socket 775 processor separately.
5.6.1. Removing the old processor
The first step in replacing the processor is to remove the old processor. To do so, take the following steps:
5.6.2. Installing the new processor (Sockets 462/A, 478, 754, 939)
The exact procedure needed to install a processor varies slightly for different processors and CPU coolers, but the general procedure is similar. In this section, we illustrate the procedure for installing a Socket 478 Pentium 4 processor, but the procedure is identical for a Celeron, and nearly so for Socket 462 (A), Socket 754, and Socket 939 Athlon 64 and Sempron processors. The only real difference is how the CPU cooler is secured, and that should be obvious to you when you examine your particular CPU cooler.
We chose a retail-boxed processor to illustrate this section. One advantage of a retail-boxed processor is that it comes with a competent CPU cooler that is guaranteed to be compatible with the processor, and typically costs only a few dollars more than the bare OEM processor. The CPU coolers that Intel and AMD currently bundle with their retail-boxed processors are quite good, especially considering the low incremental cost of buying the bundle. The bundled coolers aren't quite as efficient or as quiet as the best aftermarket CPU coolers, but they suffice for most purposes.
Our retail-boxed Pentium 4 processor, shown in Figure 5-9, includes the processor itself and a large Intel-branded CPU cooler. The plastic packaging Intel uses is treacherous. We eventually got the package open using scissors, but for a time we thought we'd have to resort to a chain saw.
Figure 5-9. The retail-boxed Intel Pentium 4 processor and heatsink/fan
The first step is to lift the arm of the ZIF (zero insertion force) socket, as shown in Figure 5-10, until it is vertical. With the arm vertical, there is no clamping force on the socket holes, which allows the processor to drop into place without requiring any pressure.
Figure 5-10. Lift the socket lever to prepare the socket to receive the processor
Correct orientation is indicated on the processor and socket by some obvious means. For Socket 478, the processor has a trimmed corner and the socket a small triangle, both visible in Figure 5-11 near the ZIF socket lever. With the socket lever vertical, align the processor with the socket and drop the processor into place, as shown in Figure 5-11. The processor should seat flush with the socket just from the force of gravity, or with at most a tiny push. If the processor doesn't simply drop into place, something is misaligned. Remove the processor and verify that it is aligned properly and that the pattern of pins on the processor corresponds to the pattern of holes on the socket.
Figure 5-11. Align the processor with the socket and drop it into place
With the processor in place and seated flush with the socket, press the lever arm down and snap it into place, as shown in Figure 5-12. You may have to Cleanliness Counts press the lever arm slightly away from the socket to allow it to snap into a locked position.
Figure 5-12. Snap the ZIF socket lever into place to lock the processor into the socket
To install the CPU cooler, begin by polishing the top of the processor with a paper towel or soft cloth, as shown in Figure 5-13. (Our editor, Brian Jepson, notes that he's become fond of coffee filters, as they are abrasive enough to polish, and so far haven't scratched anything. Plus, they don't seem to leave any debris.) Remove any grease, grit, or other material that might prevent the heatsink from making intimate contact with the processor surface.
Figure 5-13. Polish the processor with a paper towel before installing the CPU cooler
Next, check the contact surface of the heatsink, shown in Figure 5-14. If the heatsink base is bare, that means it's intended to be used with thermal compound, usually called "thermal goop." In that case, also polish the heatsink base.
Some heatsinks have a square or rectangular pad made of a phase-change medium, which is a fancy term for a material that melts as the CPU heats and solidifies as the CPU cools. This liquid/solid cycle ensures that the processor die maintains good thermal contact with the heatsink. If your heatsink includes such a pad, you needn't polish the base of the heatsink. (Heatsinks use either a thermal pad or thermal goop, not both.)
Figure 5-14. The base of the Intel heatsink, showing the circular copper area that contacts the processor
Intel never uses a cheap method when a better solution is available, and the packaging for their thermal compound is no exception. Rather than the usual single-serving plastic packet of thermal goop, Intel provides thermal goop in a syringe with a premeasured dose. To apply the thermal goop, put the syringe tip near the center of the processor and squeeze the entire contents of the syringe onto the processor surface, as shown in Figure 5-15.
Figure 5-15. Apply thermal compound
The next step is to orient the CPU cooler above the processor, as shown in Figure 5-16, keeping it as close to horizontal as possible. Slide the CPU cooler down into the retaining bracket, making sure that the lock tabs on each of the four corners of the CPU cooler assembly are aligned with the matching slots in the CPU cooler retaining bracket on the motherboard. Press down gently and use a small circular motion to spread the thermal goop evenly over the surface of the processor.
Figure 5-16. Align the CPU cooler over the processor, making sure the locking tabs on the CPU cooler align with the corresponding slots on the retaining bracket
Make sure that both of the white plastic cam levers (one is visible near Barbara's thumb in Figure 5-16) are in the open position, not applying any pressure to the CPU cooler mechanism. With the CPU cooler aligned properly, press down firmly, as shown in Figure 5-17, until all four locking tabs snap into place in the corresponding slots on the retaining bracket. This step requires applying significant pressure evenly to the top of the CPU cooler mechanism. It's generally easier to do that using your full hand rather than just your fingers or thumbs. With some CPU coolers, it may be easier to get two opposite corners snapped in first and then do the remaining corners.
Figure 5-17. With the CPU cooler aligned, press down firmly until it snaps into place
With the CPU cooler snapped into the retaining bracket, the next step is to clamp the heatsink tightly against the processor to ensure good thermal transfer between the CPU and heatsink. To do so, pivot the white plastic cam levers from their unlocked position to the locked position, as shown in Figure 5-18.
Figure 5-18. Clamp the CPU cooler into place
The thermal mass of the heatsink draws heat away from the CPU, but the heat must be dissipated to prevent the CPU from eventually overheating as the heatsink warms up. To dispose of excess heat as it is transferred to the heatsink, most CPU coolers use a muffin fan to draw air continuously through the fins of the heatsink.
Some CPU fans attach to a drive power connector, but most (including this Intel unit) attach to a dedicated CPU fan connector on the motherboard. Using a motherboard fan power connector allows the motherboard to control the CPU fan, reducing speed for quieter operation when the processor is running under light load and not generating much heat, and increasing fan speed when the processor is running under heavy load and generating more heat. The motherboard can also monitor fan speed, which allows it to send an alert to the user if the fan fails or begins running sporadically.
To connect the CPU fan, locate the 3-pin header connector on the motherboard labeled "CPU fan," and plug the keyed cable from the CPU fan into that connector, as shown in Figure 5-19.
Figure 5-19. Connect the CPU fan cable to the CPU fan connector
5.6.3. Installing the new processor (Socket 775)
Intel's current Socket 775 (also called Socket T) processors require slightly different installation steps than processors that use Socket 462 (A), 478, 754, or 939. This section illustrates those differences.
The fundamental difference between Socket 775 and other current processor sockets is that Socket 775 places the pins in the socket and the matching holes on the processor body rather than the converse. That means the pins are vulnerable, so Socket 775 motherboards use a plastic shield to protect the socket until the processor is installed. To begin installing a Socket 775 processor, simply snap out the socket shield, shown in Figure 5-20.
Figure 5-20. The gray plastic Socket 775 socket shield
With the socket shield removed, the socket itself is visible, as shown in Figure 5-21. The metal bracket that surrounds the socket is the processor retaining bracket, which is locked in place by the hook-shaped lever visible to the left of the socket. Release that lever and swing it vertically to unlatch the processor retaining bracket.
Figure 5-21. The processor socket is visible after you remove the socket shield
With the lever unlatched, swing the processor retaining bracket upward to make the socket accessible, as shown in Figure 5-22.
Figure 5-22. Release the latching lever and swing the processor retaining bracket upward
Figure 5-23 shows the two keying mechanisms used by Socket 775. A triangle is visible at the lower-right corner of the processor, pointing to the one beveled corner of the socket. Also visible near the lower-left and -right corners of the processor are two keying notches, which mate with two protrusions in the socket body. Make sure that the processor is aligned properly with the socket, and then simply drop it into place.
Figure 5-23. Align the processor and drop it into the socket
After you drop the processor into the socket, lower the processor retaining bracket, as shown in Figure 5-24. The retaining bracket is secured by the cammed portion of the latching lever against the lip visible at the bottom of the bracket. Make sure that the latching lever is raised far enough for the cammed portion to clear the lip on the bracket, and use finger pressure to close the retaining bracket until it seats.
With the bracket lip and latching lever aligned, press down firmly on the latching lever until it snaps into place under the latch, as shown in Figure 5-25. Use a paper towel or soft cloth to polish the top of the processor, as described in the previous section.
Figure 5-24. Verify that the latching lever clears the lip on the retaining bracket
Figure 5-25. Clamp the latching lever into place, securing the processor in the socket
Socket 775 uses a different mechanism to secure the CPU cooler. Rather than using a plastic bracket surrounding the socket, like Socket 478, Socket 775 uses four mounting holes arrayed at the corners of the socket. Figure 5-26 shows a typical Socket 775 CPU cooler, in this case a stock Intel unit. The white square visible at the center of the copper heatsink base is a phase-change thermal pad. If your heatsink has such a pad, you needn't apply thermal compound. If your heatsink lacks a thermal pad, apply thermal compound to the top of the processor before proceeding.
Figure 5-26. A standard Socket 775 CPU cooler, with mounting posts visible at each corner
To mount the CPU cooler, align it so that each of its four posts matches one of the motherboard mounting holes. Those holes form a square, so you can align the CPU cooler in any of four positions. Locate the CPU fan power connector on the motherboard and orient the CPU cooler so that the fan power cable is located near the power connector. Make sure the four posts visible at each corner are aligned with the mounting holes, as shown in Figure 5-27, and then seat the CPU cooler.
Figure 5-27. Align the CPU cooler so that each mounting post enters one of the mounting holes
The CPU cooler is now connected to the motherboard but not yet locked into place. Press down on the top of each of the mounting posts, as shown in Figure 5-28, to expand the tips of the mounting posts and secure the CPU cooler in position. (If you need to remove the CPU cooler later, simply lift up each of the four posts to unlock the connectors. The CPU cooler can then be lifted off without resistance.)
Connect the CPU fan cable to the CPU fan connector to complete the processor installation.
Figure 5-28. With the HSF aligned, press down firmly until it snaps into place