Mal’s Computer Corner

Platform: PC

Skill Level: Beginner to intermediate

Nerd Rating: 9 out of 10 (Project is not difficult but can result in stunning success (98%) or abysmal failure (2%))

By Malefico

There are a couple of reasons why you might replace a processor. The first, and better reason is that you want to increase the performance of your current system. If you have a computer that’s 2-3 years old, you may have noticed it’s not quite as fast as it used to be. Time marches on, and it doesn’t take very long for the CPU that was hot stuff yesterday to struggle with applications, especially games as time passes. Developers work to wring performance out of a system and new coding methodologies pop up constantly to help spread the workload out among multiple cores, so older chips with fewer cores eventually fall behind.

The second, and less positive reason is that your computer has stopped working due to a CPU failure. There are a number of ways to diagnose a faulty CPU or motherboard, too many to discuss here. However, I have included some links at the end of the article to help you find the problem yourself. The PC owner should take the time to run through the steps to make sure the part they are replacing is the problem. Catastrophic CPU failures are very rare, but when it does happen the PC owner faces a choice. Either scrap the system, or do what we nerds do which is dive in and make it better, stronger and faster than before.

While there are a number of factors involved with overall system performance, increasing processor power is definitely one way to give your system a shot in the arm. More for information than because it’s necessary, here’s a brief rundown on what sockets are and how they differ from one another. I’ll cover these in more detail in an upcoming motherboard article.

Socket Types and Processor List

PC’s generally use one of two socket types. As recently as the mid 2000’s , computer sockets only came in one flavor, PGA meaning Pin Grid Array. This configuration is still in wide use today. PGA sockets use a large number of pins, 750 to over 1000 to establish all the connections a CPU needs to communicate with the rest of the system. These pins are, well… arrayed in a grid as shown in the pic below. AMD still uses this type of socket. You’ll note a small triangle on the bottom of the AMD chip. There’s another one on the top side of the chip which points the way to another on the motherboard socket, making it easy to tell which way to orient the processor during installation.

Meanwhile, Intel recently shifted to using LGA, or Land Grid Array sockets. There are still pins involved, but not on the CPU itself. Instead the CPU has lands, over 1100 tiny depressions on the bottom of the processor. Properly installed, these lands contact pins which are sticking up out of the motherboard itself. As you can see by the photo below, the two types of sockets are easily distinguishable. Also note the two slots on the Intel chip. They match up with the motherboard socket and ensure the processor is oriented correctly during installation.

Finally, you have BGA, or Ball Grid Array. This is the kind of mounting system that’s used in small devices like smart phones or tablets, some laptops and dedicated devices, like POS (Point Of Sale) systems, ATMs, and others including game consoles. BGA is used on devices where the manufacturer has not chosen to make the CPU serviceable by the user. Reseating a BGA chip requires that you first own or have access to a BGA Rework Station ($800 ot over $3000 depending on quality and automation), an IR or hot-air heating device and the technical knowledge required to safely remove and clean the old solder and flux, and place the new balls with a template, then heat them to adhere them to the chip and heat once again to solder the chip to the board.

Let’s talk about compatibility for a moment. In the table below I list a number of common sockets and compatible processors. First, I want to say the list is not exhaustive, but rather offers the most common processor/motherboard combinations. Second, it’s important to check each motherboard’s compatibility by visiting the manufacturer’s website and looking for the CPU Support List. If you have a brand-name PC, you may have to go the that company’s site instead, as many large PC builders order custom motherboards and are therefore the ones to see about CPU compatibility.

Another important note is that a BIOS update may be required before your board will recognize a processor upgrade. For the vast majority of folks installing a new CPU this is not an issue, simply determine the BIOS version that supports the CPU you want to install and then follow the instructions for updating BIOS. For those who have to replace a CPU due to failure, you still have a couple options. The first would be to locate a used, working processor of the same exact type, or at least the same series as the one that broke and install it for the purpose of updating BIOS to the version required for the one you want. Or find the most competent CPU that your BIOS does support and limit your upgrade to that one for the time being. For instance, the POS is running a lowly Athlon II X2 250. processor. Without updating BIOS, on my board I could upgrade to any Athlon II X3 or X4 processor, or Phenom II X2/X3/X4/X6. That leaves a lot of room for improvement without going through any extra steps.

In the wide world of PC hardware, most owners will have a number of options regarding replacing/upgrading their CPU. The table below lists AMD and Intel sockets that are in common use today. Common AMD sockets are AM3, AM3+, FM1 and FM2. Intel sockets in common use include LGA 1150 and 1155.. Older (or less common) sockets are AM2/AM2+ (AMD) and LGA 1156 (Intel). These are by no means the only sockets out there, but are the ones most widely used in big-factory towers like Dell, Gateway and HP and the most commonly available for PC hobbyists.

Replacing the CPU

Tools you’ll need:

Philips screwdriver

Small flat head screwdriver

OR bit driver with Philips/Flat bits

Thermal compound/pad (for used processors, or new ones that are sold without heat sink/fan)

After you’ve chosen the right processor for your needs, it’s time to dive in and change the chip. As with any PC project, you’ll want to unplug the tower entirely from the wall and all peripherals. Remove the side panel of your case, then depress the power button for at least ten seconds or until the power LED indicator on the board goes dark. Ground yourself using and anti-static strap, mat or both, or remember to touch yourself or a tool to a metal surface within the case each time before touching any components. Seriously, spend five bucks on a strap.

Unplug from the PSU

In order to clear a space around the CPU, remove the ATX 20/24 pin, the ATX 4/8 pin, and the CPU fan connectors running from the power supply. For descriptions of these and the first steps in this procedure see my Guerilla Gaming article. For the CPU fan harness, gently insert the small flat head screwdriver to move the latch away from the connector before pulling it free. Drape all these cables over the side of the case and out of the way.

Remove the CPU Fan

Next, remove the CPU fan by taking out the four small Philips screws or using the flat head to move the locking tabs out of the way of the fan housing. Set is aside so you don’t confuse it with the new unit. So far, this has been similar to the cleaning procedure.

Remove the Heat Sink

Now, it’s time to remove the heat sink. You can’t miss this, it’s the large block of vaned metal underneath the CPU fan. Usually, this part is held in place by a locking mechanism of some sort. These designs vary depending on the manufacturer and time period of the piece. If you are having trouble figuring out how to remove the heat sink lock, try going to Youtube and entering the brand/model of your system followed by “remove heat sink”. In most cases some helpful soul has posted a video showing exactly how to remove the lock.

In about 95% of all PC’s the heat sink will come loose with some gentle pressure. Unfortunately, some big builders occasionally use a compound that seems to be part thermal paste, part cement because the CPU is stuck fast to the heat sink. In any case, the best way to remove a heat sink is to grasp it in both hands and move it like you were trying to open/close a jar lid. It should come free of the CPU with little effort. If it is stuck, keep up the movement but ratchet up the force until it does pop free. DO NOT rock the heat sink up and down or insert a screwdriver or other tool underneath the heat sink in order to pry it up off the CPU as processor/mptherboard damage can result. In extreme cases, if the heat sink is sufficiently stuck to the CPU, damage to the CPU/board can result even though you used the correct technique, but this is almost unheard of and has never happened to me.

Worst case scenario, you’ve been unable to remove the heat sink or are unwilling to apply enough force to break it loose from the CPU within the confines of the case. You can always pull up on the heat sink, yanking it and the processor out of the socket, but CPU damage can result. If you have to do this, see the section below on techniques to get the CPU loose if they both come out together.

Separating CPU and Heat Sink

If you were unable to remove the heat sink separately from the processor, the best way to unstick them is to get a small glass bowl just wide enough to allow the processor to pass the edge, but small enough so the assembly is suspended by the heat sink. Fill the bowl with 91% isopropyl alcohol (rubbing alcohol but make sure it’s not the 70% stuff). Set the stuck assembly inside the bowl making sure the alcohol entirely covers the processor. Leave it there for at least fifteen minutes then try to separate the two. They should come apart pretty easily at that point.

Remove the CPU

Once you’ve removed the heat sink, set it aside and locate the socket locking lever and move it to the vertical position. Then, grasping the processor by each corner lift it straight up out of the socket. If it was functional when you started, check for any misalignment of the pins on the bottom. If any are bent, see the last section of this article. You can lay it on any non-conductive surface, top side down, until you can store it safely later.

If you bought a new processor, chances are it is packaged with a new heat sink and fan. Unless you are overclocking, these pieces are usually adequate. The new processor will come in a little storage case designed to protect the delicate underside of the unit.

Install the New Processor

Remove the new processor from its storage case, align the triangle marks or socket slots, and grasping it again by each corner lower the new chip into the socket keeping it as flat as possible. It should easily drop into the socket. Modern processors from AMD and Intel use ZIF technology in their sockets. ZIF stands for Zero Insertion Force, meaning that you should never have to apply ANY downward force to get the processor into the socket. If it doesn’t drop into the socket freely, it’s not aligned properly. Lift it up, readjust the position and lower it again.

Once the CPU is in place, lower the socket locking arm and secure it in the locked position. Gently check that there is no movement of the CPU within the socket.

You can then take the old CPU and store it in the new chip’s storage case. Remove the new heat sink and fan from the package, noting any difference in the locking mechanism for the sink. These will be minor since they are designed to fit the same socket. Whenever the thermal interface between CPU and heat sink is broken, it’s necessary to reapply a thermal compound. Check that the bottom of the new heat sink has a thermal pad applied to it. It may be a simple square, or be applied in a more elaborate fashion, but all sinks that are packaged with CPUs should have some applied. If for some reason you don’t see a pad, look inside the package for a small tube of thermal paste.

Apply Thermal Compound

Thermal compound is an electrically non-conductive but thermally conductive paste that serves as the first part of the CPU cooling system. Since no man-made surface is entirely smooth, it fills the air gaps between CPU and heat sink and allows heat to travel away from the processor to the heat sink, and from there allows the fan to dissipate the heat into the interior space of the case.

Applying it is a simple matter. Two main things to remember here are that less is more, and instead of putting it on the heat sink you will apply the paste to the top of the CPU. The smallest tubes of commercially available thermal paste are 4 gram syringes. This is enough paste to cover 3-4 processors, so the mass of paste that you will use is very small. With the CPU locked in the socket, push some out of the syringe (there are marks on the side to indicate how much you are squeezing out) onto the CPU cover.

Wrap your finger in a bit of plastic wrap, push your finger into a thin sandwich bag or cut off the finger of a rubber glove and smear the paste around on the CPU case until it no longer spreads. Apply some more if necessary and continue to spread the paste until the entire top of the CPU has a smooth, thin layer of the paste on it.

While it’s impossible to create a perfectly smooth surface, do your best to avoid any obvious lumps of paste. And thin means THIN, approximately .003”. Basically, know that what you are trying to do is fill microscopic differences in the two surfaces with paste instead of air and don’t just squirt the whole tube onto your CPU. The more paste you use, the less effective the interface is because the paste does not conduct heat as well as the metal surfaces it joins, and any excess is just going to run out over your motherboard when the paste heats up.

If you need to apply thermal paste to your CPU without replacing it, remove the chip from the socket and apply some 91% (not 70%) isopropyl (rubbing) alcohol a clean, soft rag or cotton ball. Holding the processor carefully, scrub the residue of the old paste off the top of the processor, then clean the bottom of the heat sink the same way. Continue by following the directions above.

This is by no means the only method to apply paste. To get an idea of what happens when you have too much time on your hands, check out this article.

There are a number of good-quality thermal compounds/pads sold today. I use Arctic products because they work well and are reasonably priced. They perform much better than the brand X stuff applied at the factory- I typically see a 5-7 degree (Fahrenheit) improvement at idle and 10-15 degrees or more under load.

CPU Damage: Can you fix it?

This section is written in case the project did not go as planned. Whether the CPU sustained damage as a result of excessive force removing it, or maybe you accidentally dropped it, don’t panic (yet). This section mainly applies to AMD and much older Intel chips that use pins instead of lands. If you notice any obvious damage on the bottom of a CPU, take a closer look. If any of the little pins are bent, irreparable damage may have occurred.

There is a technique you can use to try to repair the chip in lieu of buying another right away. First, using a small needle, ground the needle on the case and then use it to bend any pins that are so bad they are touching another or are bent diagonally from the array. Use just enough force to move the pin so that you can employ in the next step.

Go through your wallet/purse and find a plastic card just thin enough to fit between a normal (unbent) row of pins. Using the side that does not have a magnetic strip, if applicable gently push the card down into the bent row and move it until the pins are back in the right place. Then turn the card 90 degrees and run it along that same row. Repeat this process until you have inserted the card into each bent row from both directions. If any of the pins will not straighten entirely with one card, sandwich them between two cards, again straightening from both directions. I’ve personally saved a couple processors this way, so it does work.

If any of the pins on the processor are broken, please see alternate method B, below.

Alternate Method B (Plan Beezy)

If the CPU with broken pins was broken before, or is the one you were going to replace anyway, please dispose of it thoughtfully. If it is the new CPU, return to the place of purchase and buy another one.

Seriously, if some of the pins are broken/missing, then you have a whole other set of problems we’ll discuss in an upcoming article on motherboards.

Here are some links to articles that go into detail about how to diagnose CPU problems and differentiate them from motherboard issues.

The first talks about simple procedures you can follow using tools that are included as part of the BIOS or OS:

http://www.linuceum.com/Hardware/hwPrbCPU.php

This one has a flowchart that gets more involved:

http://superuser.com/questions/228946/any-way-to-tell-apart-a-cpu-defect-from-a-mainboard-defect