CPUs

A CPU, or central processing unit, is the brain of any computer. More commonly called the processor, the CPU performs most of the actual calculations in a computer and has a large impact on speed and power. There are two main components to a typical CPU: one is the arithmetic logic unit (ALU), which performs arithmetic operations. The other component, the control unit (CU), takes instructions from memory and decodes and executes them, calling the ALU when needed.

CPU VARIATIONS:

Most processors on the market are made by Intel or AMD, and there are scores to choose from. You can see the make/model of a CPU by the text on it's front surface.
Some different variations of a CPU include:

- Single, Dual and Quad core processors: A CPU core is the the part of a CPU which performs operations. CPUs with multiple cores can perform more calculations at once, due to their ability to designate different tasks and distribute workload over multiple cores.

- Mobile processors: Processors in mobile phones must be smaller and more efficient at dissipating heat, as well as being power efficient - all while having satisfactory processing power. This means mobile CPUs typically use far less power, and don't perform well in benchmarks compared to even low end desktop CPUs.

- 32 bit vs. 64 bit: While any new processor within the last decade has a 64 bit architecture, 32 bit processors are still around, and there is a difference. 64 bit processors use 64 bits (8 octets) for memory addressing and processing, while 32 bit processors us 4 octets. -

- Socket: The largest factor of compatibility between your motherboard and CPU is your motherboard's CPU socket. The socket of a CPU determines what motherboards it can fit in. For instance, an AM3 socket CPU can fit in an AM3 socket motherboard, or and LGA2011 CPU can fit in an LGA2011 socket motherboard.

- Speed (GHz) - For every CPU, there will be a number by the name followed by GHz. This is a measurement of the speed of the front side bus (FSB), or at least a ratio of it. The higher the number, the better - a higher FSB speed means the processors works faster, although the processor is usually faster than it's buses.

Labeled Exploded View:

CPU DIAGRAM (see above)

http://www.build-your-own-cheap-computer.com/image...

The CPU has 4 major components on this diagram: The ALU, the CU, the registers and the internal memory.

- The control unit (CU), as mentioned, takes instructions from memory and decodes and executes them, calling the ALU as needed to perform calculations.

- The arithmetic logic unit (ALU), as discussed before, performs all arithmetic and logical operations.

- Registers are very important to the modern processor. Registers usually have of a small amount of fast storage, although some have specific functions for certain hardware, and may be read-only or write-only. This is the fastest way to access any data.

- The processor's internal storage, or cache, has multiple levels of data storage (mainly L1, L2, and L3). This is used for faster access, to reduce the average effort to access data from the main memory or RAM.

Proper Maintenance and Care:

When dealing with a CPU, it's very important to be incredibly careful, especially if you're handling it physically. In terms of physical care, there's really only a few ways to care for your CPU. One is to make sure that whenever you do take your CPU out, be very careful with the pins, and make sure not to drop it. It takes an incredibly small amount of force to bend a pin and put your processor out of commission.

Another important part of CPU maintenance is making sure your CPU is being being cooled properly. You can check the temperature of your CPU with some very common applications, like the software Speccy, which shows you the specs and temperature of your computer hardware. To keep your processor running around the ideal 45 degrees C, some important steps are to clean your computer case out, which keeps ventilation going, and replacing the thermal paste on your processor. You can get dust out with canned air easily. This alloy compound helps dissipate heat from the processor before being sent up through the heat sink. I will be showing you how to replace the thermal paste later - all you need is thermal paste, paper towel and a little rubbing alcohol.

Diagnoses and Troubleshooting of Common Issues:

Luckily, there isn't much troubleshooting to be done for CPUs. Since CPUs are so essential for the operation of a computer, any problem can become a huge hindrance, and many safe guards are in place. It is very rare for a CPU to fail on its own - however, there are several very common problems when it comes to any CPU.

Bent Pins: If you're trying to replace your CPU or remove it from the socket, there's a chance some pins on the bottom of the CPU may bend or break. This is a major problem, because if even one pin is bent it can stop the entire CPU from functioning or even fitting into the motherboard's CPU socket. If you examine the CPU carefully and discover that some pins are bent, you may try to straighten the pin out VERY CAREFULLY with something very small, like a mechanical pencil. However, if you can't straighten the pins out, the CPU is busted - you'll have to replace it.

Overheating: If your computer frequently shuts off without warning, your computer may be overheating. Your computer may display a "system temperature" error on start up, or you can even check with Speccy, mentioned above. The shutting down of a computer is the CPU protecting itself, so the heat does not damage it. Overheating can have several causes. One possibility is that the thermal paste is old, and not dissipating heat from your processor effectively. Thermal paste is the compound between the CPU and the heat sink (the cooling system). A way to keep the thermal paste from losing it's effectiveness is to replace regularly as part of maintenance. Another possibility is that the fans and case are clogged with dust and the case is not being aerated enough. You can solve this issue by opening up your computer's case and making sure the ventilation is free from dust or dirt.

If your CPU isn't working, and these are not the correct issues, then your CPU may have experienced an electrical surge and fried. Unfortunately, the only solution to this is buying a new processor. However, outside of these external factors, it's very unlikely a CPU will fail on its own - and if it does, it's dead. All that's to be done is to buy a new processor.

To begin replacing your thermal compound, you're gonna need to open up the case to get to the motherboard and processor.

Next you'll need to unplug the fan for the heat sink from the motherboard. This plug will be labeled "CPU FAN", if you can't find it.

Now you'll need to flip the lever on the heat sink, which is on one side over the metal latches. This lever is what's holding your CPU and heat sink tightly to the motherboard, but you'll need to remove this to access the CPU. The last step to removing the heat sink is detaching the two latches on the side of the heat sink from the motherboard so you can lift the heat sink away from the motherboard.

Now that the heat sink is no longer held onto the motherboard, carefully lift it away to reveal the CPU. You may need to un-stick it a little bit, because the thermal paste may make it sticky or require more effort to remove.

Now that the CPU is revealed, you can loosen the socket by lifting the latch into a 90 degree position, until it clicks into place.

Very carefully remove the CPU by lifting it straight from the socket. To clean the old thermal paste off, use some paper towel and rubbing alcohol. Make sure to hold the CPU by the edges while you scrub, and handle it carefully and don't drop it. You don't want to bend any pins or damage the CPU.

Make sure to clean the bottom of the heat sink with alcohol and paper towel as well, because there will be more thermal compound there. If it's left there, replacing your thermal compound on your processor won't be as effective due to the left over old compound.

Put the CPU back into it's socket gently, setting it down straight and making sure the gold corner on the edge of the CPU matches up to the triangle on the CPU socket. Press the latch back down to secure the CPU back in place.

Now is the time to put the thermal compound back onto the CPU. Use about a pea-sized drop on the center of your CPU - not enough and the thermal paste won't cool your processor enough, too much and it may spill over onto the motherboard.

By pressing the heat sink down onto the CPU, you spread the thermal paste out on the surface evenly. To secure the heat sink back in place, simply re-do the metal latches on the side and flip the lever to the secured position.

An easily forgettable step is forgetting to plug the heat sink's fan back in - however, if you don't plug the fan back in, then your PC's not gonna be cooled properly (obviously).

Now that your heat sink is plugged back in, you're ready to go! You can close your case back up and start using your computer again.