Introduction: What Is a CPU, What Does It Do, and How to Troubleshoot It

Everyday you here the terms "CPU" or "Processor" being thrown around, but do you really know what it means?

I will go over what a CPU is and what it does, then I will go over common CPU issues and how to possibly fix them.

Step 1: General CPU Info

  • CPU stands for Central Processing Unit. This term can really be applied to any processor, such as a micro-controller on an arduino, or the ARM core in your CPU. But for this, I will be talking about desktop CPUs.

  • This is the brains of the Computer. The CPU does a majority of the math in a computer.

  • A CPU contains hundreds of millions of incredibly small transistors. These transistors act as logic gates to do calculations to run programs.

  • Modern CPUs are often contain multiple cores. Each core can do a separate task from the other cores. It is far more efficient to pack several processing core units onto a single die that can fit into one socket, rather than have a motherboard that requires several entirely separate CPUs to be inserted.

  • Each CPU core gets a very small, very fast, amount of memory. This memory holds very frequently used programs, and current running processes. Using memory so close to the cores is better than having to continuously transfer data from the system RAM back a forth.

  • The CPUs clock speed is is a measure of how many clock cycles aCPU can perform per second. Modern day CPUs are so fast they are measured in Ghz.

  • Types of CPUs: There are two main producers of CPUs.

    AMD generally produces processors that are more affordable. While Intel produces higher end CPUs that are normally more expensive

  • AMD and Intel also use different sockets. Intel uses an LGA socket which stands for land grid array. LGA sockets have the pins in the socket and contact pads on the CPU itself. AMD uses a PGA socket which stands for pin grid array. PGA has the pins on the CPU, and the pins fit into slots in the socket.

Step 2: CPU Components

Core - These are the logic centers of the CPU. There are normally multiple cores in a modern day desktop computer. Each core gets its own L1 and L2 cache of memory for its current process.

Cache - This is the on board memory of the CPU. This memory is much faster than system RAM. There are 3 levels of cache, L1, L2, L3. Each processing core on a multi-core CPU gets its own L1 and L2 cache. The whole CPU has one large L3 cache that all the cores have to share.

Memory Controller - a digital circuit on the CPU die that manages the flow of data going to and from the computer's system memory.

PCIe Controller - a digital circuit on the CPU die that manages the flow of data going to and from PCIe expansion cards.

Misc IO Controller - This is a digital circuit on the CPU die that manages the flow of data to and from IO devices on the motherboard

Step 3: CPU Maintence

  • The most important thing for a CPU is adequate cooling. A CPU needs to keep its temperatures relatively low in order to work properly. Keeping the temps low also increases the life span of the processor. The component for cooling a CPU is called a heatsink. A heatsink makes contact with the CPU using thermal paste, then the heat is transferred to fins attached to the heatsink. The heat is then dissipated by the fins. Another way to cool a CPU is using liquid cooling. This works by having a water block contact the CPU, then water in tubes flows over the block and transfers heat to a radiator where the heat is dissipated. Water cooling often produces the lowest temperatures, but is far more expensive than a regular heatsink.
  • Every so often, you will need to take your heatsink or water block off to clean off the old thermal paste and put new paste on. This is because over time the thermal paste gets hard and crusty and does not transfer heat well
  • You can use software to tell if your CPU is staying at adequate temps. This will tell you if you might need to replace the thermal paste
  • When working on the hardware of a PC, try to avoid messing with the CPU as much as possible. The CPU is a fairly delicate component. The pins on the CPU or the pins in the CPU socket are prone to bending, and they are so small it is very difficult to bend them back. Also make sure not to statically electrocute the CPU, as that is not hard to do, but can be devastating.

Step 4: Common CPU Problems

  • Since the CPU is the main processing unit in your computer, it can often be the cause of your strife. The most common issue people get is their computer slowing down. This is normally caused by RAM or your HDD. But, if this is happening on a laptop, I can be a result of your CPU over heating. Laptops cannot get rid of heat as easily as a desktop can. And because of this, CPUs in laptops tend to thermal throttle. Thermal throttling is when a CPU slows itself down to prevent overheating. If this is happening in a laptop, the best thing to do is to move the computer into a cooler room. But if overheating and thermal throttling is happening on a desktop, then you should try getting a new CPU cooler. And/or replacing the thermal paste.
  • An overheating CPU could also cause the system to prematurely shutdown either in use or when starting up. This only happens in the most extreme cases of overheating. The CPU gets so hot it shuts off power to save itself.
  • If the computer does not start up, this could be a failed CPU or an improperly seated CPU.
  • It is recommended to try using some third party software to check what could be going on with your PC. This could give you some insight before you go digging through your hardware. Of course, this software is only useful if you can reach desktop and stay there long enough to use it.

Step 5: How to Clean Your CPU and Apply New Thermal Paste

Step 1: Remove the heatsink. This step varies by which heatsink you have. If it is the default intel heatsink, then you need to twist the 4 tabs around the heatsink to remove it. If it is the default AMD heatsink, then there will be a latch on each side of the heatsink, and one of the latches will have a lever. You need to release the lever, then wiggle the latches off. When pulling the heatsink off, it may be stuck on the CPU. DO NOT FORCE IT, you may end up ripping the CPU out of its socket. The best way to get by this is by removing the heatsink right after you have used the PC, but make sure it is not hot enough to burn you.

Step 2: Clean the CPU. To clean the CPU, you will need a bottle of isopropyl alcohol and a microfiber clothe, a glasses cleaner that you are not using will do. Apply some alcohol to the clothe, then rub the CPU. Keep doing this until ALL traces of the old thermal paste are gone. It is recommended to keep the CPU in the socket while doing this, as that way you will not have to worry about bending pins.

Step 3: Apply new thermal paste. The thermal paste you buy should come in a syringe, and you simply squirt a half-pea to full pea sized glob onto the CPU. Do not do any per-spreading, as this does not help with heat transfer. Make sure to not apply too much paste, because if too much is applied to the point it overflows onto the motherboard, and the paste is metal based, you can short circuit and fry your motherboard. Also, do not apply too little, as then you might still have overheating issues.

Step 4: Put the heatsink back on. This step is fairly simple, just do step one in reverse. However, when making contact with the CPU, make sure that you press straight down, do not put the heatsink on at an angle. And try not to twist and turn your heatsink too much once you've made CPU contact.