This chapter is from the book
This chapter is from the book
This chapter is from the book
Troubleshooting CPUs
The most common issue with a CPU is when it isn’t installed properly or securely. An improperly installed CPU could possibly cause a complete failure when you try to turn on the system. This failure might be accompanied by a series of beeps from the POST. If this happens, always check the power first, just in case. Then check the main power connections and then the 8- or 4-pin CPU power connection. Another possibility is that the system might turn on and power might be supplied to the system, but nothing else happens: no POST, no display (meaning a blank or black screen), and no drive activity. In any of these situations, after checking power, make sure of the following:
Ensure that the fan is connected and functional: Some motherboards have a safeguard that disables booting if the fan is defective or not plugged in. Or you might get a message on the screen or another type of warning, depending on the motherboard. Be sure that the fan is plugged into the correct power connector on the motherboard (or elsewhere) and verify whether it turns on when the computer is on. If the fan has failed, purchase a replacement fan; just make sure that the new fan is compatible with the heat sink and motherboard.
Check other major components: Remember that the CPU is a part of a bigger system—one in which other components are more likely to be the cause of many problems. These components include the video card, RAM, and motherboard. Be sure to check these other components for simple connectivity problems, which could be the actual culprit. Always check connections first before taking apart the CPU assembly.
Make sure the heat sink is connected properly: Make sure that the heat sink is flush with the CPU cap and that it is securely fastened to the motherboard (or socket housing).
Ensure that the CPU is installed properly: Make sure it was installed flush into the socket and that it was oriented correctly. Of course, this means removing the heat sink. If you do so, you should clean off excess thermal compound and reapply thermal compound to the CPU cap before reinstalling the heat sink.
Following are a few more possible symptoms of a failing CPU:
Unexplained crashes (shutdowns) occur during bootup or during use.
The system locks after only a short time of use.
Voltage is near, at, or above the top end of the allowable range.
Sometimes a CPU is just plain defective. It could have been received this way, or maybe it overheated. Perhaps there was a surge that damaged it, or maybe someone overclocked it too far, and it was a victim of overvoltage (and subsequent overheating). Regardless of the culprit, the CPU needs to be replaced. Now, by default, CPUs come with a heat sink and fan, and you can install the CPU as you normally would. But in some cases, you can save money by purchasing only the CPU and using the existing heat sink. In this case, remember to clean excess thermal compound and then reapply thermal compound; but reapply it to the CPU cap and not to the heat sink. If the CPU was installed properly, users don’t usually have many problems with it (unless they are overclockers). Keep this in mind when troubleshooting the CPU or when troubleshooting an issue that appears to be a CPU issue but that might actually be something else altogether.
On a lighter note, sometimes you might get reports from customers about unusual noises coming from inside a PC—a buzzing of sorts (or perhaps even a grinding noise). The noise could be caused by a wire or cable that is brushing up against the CPU fan (or other case fan). Be sure to reroute cables inside the computer so that they are clear of the CPU and any other devices. This will also aid with airflow in the PC and keep the PC cooler. The CPU fan might also make noise due to being clogged with dust, especially in dirtier environmental conditions. If the fan is still functional, you can use compressed air to clean it out. But be careful because too much air movement could cause a static discharge. For example, if the CPU fan (or case fan) is moved due to the air flow of a compressor, it could cause ESD. Use a piece of foam or other plastic stopper to keep the fan(s) in place while you use compressed air. Keep a computer vacuum handy to clean up the mess, if necessary; we’ve seen computers that had so much dust and dirt inside it could fill a garden! But be careful with computer vacuums and air compressors. Use a plastic nozzle or tip (never metal) and don’t actually touch any of the components.
