PC Troubleshooting - Symptoms of a Bad CPU PC Troubleshooting - Symptoms of a Bad CPU

It's very difficult to determine if a failure is caused by the CPU because many other components can cause the same symptom when they fail.

1. System fails to boot
2. System re-boots intermittently
3. General Protection Fault
4. Illegal Operation
5. Stop Error, or BSoD (Blue Screen OfDeath)

Actually, CPUs rarely fail, and about the only way to determine if the CPU is causing the failure is to swap it out with a known working CPU of the same type and speed. Since this is difficult, the best bet is to first rule out every other possibility.

Before suspecting the CPU, rule out all the possibilities listed below.

1. The Operating System
2. A peripheral port device
3. A bad memory module
4. The hard disk drive
5. The power supply
6. The motherboard

The Operating System

If your computer is not totally crashed, there are various methods you van use to restore the operating system. The most decisive is to restore the system back to factory settings. This might be considered the "nuclear" option because all the applications that you installed and all the documents that you created will be lost. But this would eliminate the operating system as a possible cause of the problem.

For example, HP places a factory image on the system partition and provides a "System Recovery Manager" utility to restore that image. To use this method; while Windows is starting, repeatedly press the [F11] button, and when the HP Recovery Manager screen appears, select "System Recovery".

All major computer manufacturers provide a similar method to restore your operating system back to the way it was when you first took it out of the box. After that, the first application you'll want to install is an antivirus program.

A Peripheral Port Device

You can start by unplugging all peripheral devices. See if the system operates correctly with all peripheral devices unplugged. If so, reconnect one peripheral device and see if the system still operates correctly. Reconnect one peripheral device at a time until the problem reappears. Unplugging and reconnecting peripheral devices is easy, but unfortunately there’s more to it. Each peripheral device has an associated device driver.

A device driver is a piece of software that interfaces a hardware device to the operating system. It's possible for a device driver to get corrupted or hacked. If your computer is not totally crashed, you can use Device Manager to Update, Disable, or Uninstall a device driver to eliminate it as a source of the problem.

Right-click on the Windows button and in the menu that appears, select Control Panel. In Control Panel select the Systems icon, and in the left panel of the System page that appears, select Device Manager. In the Device Manager window that appears, select a type of device that might possibly cause the problem, and click on the greater-than icon to expand the branch and see a list of specific devices.

If you right-click on a specific device, a menu will appear where you can select to Update, Disable, or Uninstall a device driver. You can also select Properties, and in the Properties dialog box that appears, click on the Events tab to see if any error events occurred. Using this method you might be able to fix a device driver that is causing the problem, but there are many device drivers on any system, so replacing them one at a time would be very time consuming.

A Bad Memory Module

A defective RAM stick can cause really weird problems. If your mother board has multiple RAM slots, you can remove the RAM from the higher number slots and see if that solves the problem. A system can generally run without a full bank of memory. If not, remove the RAM from the lower number slots and replace it with the RAM that you removed from the higher number slots. You can also purchase new RAM that is the type your system requires.

If you have ruled out out all the other possibilities, investigate the items listed below.

1. Overheating
2. A short circuit
3. ESD

The Primary Killer of CPUs is Heat

Check the items listed below.

1. The CPU fan is operating
2. Case exhaust fans are operating
3. No fan or vent is blocked with dirt
4. CPU fan air flow is not blocked by cables
5. There's sufficient space around case fans and vents for proper air flow

Visual Inspection

Visually inspect the CPU for mechanical problems. Some of these inspections may require removal of the CPU fan and CPU.

CPU with fan
CPU with Fan

1. The CPU fan is securely fastened to the CPU
2. The thermal compound between the CPU and heat sink appears sufficient
3. Dirt or spilled liquids are not causing a short between pins or traces
4. The pins of the CPU are making positive contact with the circuit board

Note that modern CPUs use ball grid array (BGA) packaging. With BGA packaging, the pins are replaced by balls of solder stuck to the bottom of the package. The CPU is placed on a circuit board pads in a pattern that matches the solder balls. The assembly is then heated causing the solder balls to melt.

Another killer of CPUs; ESD and Power Surges

Electrostatic discharge (ESD) is a spark that jumps from a technician's or other person's hand when they're working inside the computer case without the proper ESD protection. The sad thing is that the effect of an ESD may not appear immediately after the ESD. The CPU may work for a while until heat and electrical signals in the CPU finish off the damage.

A power surge can occur if lightning strikes a power line, or if a mechanical device like a cloths washer motor stops. Good power supplies have surge protection built-in, but they can only absorb a few strong surges, then they no longer provide protection.

BIOS Beep Codes

A computer's BIOS (Basic Input Output Service) contains code that performs a POST (Power-On Self Test) every time you start the computer. If the POST determines that the computer is damaged to the extent that it can no longer communicate through the display, it will attempt to communicate information about the fault through "beep codes". A computer that emits more than a single beep at power-up is trying to tell you something.

To decode the beeps, you'll need to determine what kind of BIOS your computer contains. You can learn this from the information that came with your computer or you can read the information printed on the BIOS chip itself. For example with most AMI (American Megatrends International) BIOS, 5 or 7 beeps means a bad CPU.

What to Do About a Bad CPU

If you have ruled out all other possibilities and you are confident that you have a bad CPU, then you can replace it with a new CPU of the same type and speed. Sometimes you can upgrade your motherboard with a more powerful or faster CPU, but make sure that your motherboard and system memory are compatible with the new CPU. Make sure that you mount the CPU heat sink and fan and properly and use adequate thermal compound between the CPU and heat sink. Consider upgrading to a new motherboard/CPU combo.

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