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[ The PC Guide | Troubleshooting and Repair Guide | The Troubleshooting Expert | Troubleshooting Specific Components | Troubleshooting the Processor ]

There appears to be a failure with the processor

Explanation: The system processor appears to be either dead, impossible to boot up, or not functioning properly.

Diagnosis: There are many possible reasons why a processor can appear to have failed. In the real world, outright processor failures are very rare, especially if the processor has worked in the past (unless we are talking about a very old CPU, more than ten years of age). If the processor works for the first month that it is installed, it will probably last for five or more years, as long as it isn't abused. Problems with processors are far more likely to be misconfigurations, overheating problems, or misdiagnoses of other failed components.

Recommendation:

  • If you have recently assembled this PC, or you have recently performed an upgrade to it, check here for possible general problems.
  • If you have an extra processor available for a quick test, try swapping the processor with the other one and see if the problem clears up. If it does, then put the original processor back in again and see if the problem returns. If it does, then you can feel pretty confident that the processor was probably bad. I only recommend doing this early in the troubleshooting process if it is convenient (most people don't have an extra processor handy for this sort of test). You may also want to try the processor you swapped out of your system in another one, as another test of what it is that is bad.
  • Check to see if the processor is overheating. After the PC has been running for a while, open it up, and turn it off. Then ground yourself and touch the processor carefully, or part of the heat sink near the processor. If you cannot leave your finger on the processor for more than a few seconds due to the heat, the chances are good that the CPU is overheating. Diagnose this here.
  • Make sure that the processor is tightly inserted into its socket and that is has been inserted correctly and not rotated in the socket somehow (this is not generally possible with newer chips anyway).
  • Double-check the jumpers (or BIOS settings for a jumperless system) that tell the motherboard which processor you have in the system, to make sure that they are correct. Setting the jumpers incorrectly can cause the processor to malfunction, because you may be accidentally overclocking it or telling the motherboard that it is from a different processor series than it actually is.
  • If you are configuring a Cyrix processor that uses a "P rating", remember to set the chip up using its real clock speed, not the "P rating" number, which is just a benchmark. For example, the Cyrix 6x86-PR133+ is not a 133 MHz chip. It runs at 110 MHz and should be configured with a bus speed of 55 MHz and a clock multiplier of 2. Setting it up as a 133 MHz chip would mean you were overclocking it and this can cause a host of problems.
  • Double-check the voltage settings for the board. In particular, the voltage requirements for some of the chips, such as the Pentium with MMX, Cyrix 6x86L and 6x86MX, and AMD K6, differ from the standard 3.3 to 3.5 volts used by the original Intel Pentium processor. They require a split-rail or dual voltage. Many older motherboards do not support these CPUs.
  • In general, make sure that you are using a processor that is supported by your motherboard. If the processor you are trying to use in the motherboard was not established in the market at the time you bought the motherboard, and you don't see it specifically listed as supported in the motherboard manual, it may not be supported even if the processor's manufacturer claims it is "compatible". You may need a BIOS upgrade to use the chip. Contact the motherboard's technical support department and tell them what chip you are trying to use, and ask them what you need to do to make the board support the CPU.
  • Apparently, non-Intel CPUs will not work in some Intel motherboards, which specifically check the CPU type and refuse to boot if they find anything other than Intel there. Note that this applies only to Intel motherboards, not all motherboards using Intel chipsets (of which there are hundreds of varieties). I am not sure how many different Intel motherboards this applies to.
  • If you are running the Cyrix 6x86, make sure that you are using a motherboard that is approved for the chip! Not all motherboards will support it, and the number one reason why is that the chip is too demanding electrically. A board with incorrect support for the chip may overheat or cause the chip to malfunction.
  • Incorrect or overly-aggressive BIOS settings can cause processors to behave strangely. Try toning down the BIOS settings to conservative or default values and see if the problem clears up.
  • Try to disable the secondary cache in the BIOS setup. This may fix the problem (but usually will not). If it does, there is likely a problem associated the secondary cache.
  • Try to reduce the speed of the processor to see if that fixes the problem. For example if you are running a Pentium with MMX at 200 MHz, try changing the motherboard to run it at 166 MHz. If the problem goes away, then the chances are strong that the problem was due to overheating and should be corrected before you try the processor at the higher speed again. If the processor will only run at a slower speed, it is possible that you have unfortunately purchased a remarked CPU, although this is far from a conclusive test.
  • Try swapping the processor with another and see if the problem clears up. If it does, then the processor was probably bad. If it doesn't, you need to look elsewhere.
  • If the processor doesn't in fact appear to be the cause of the problem, try troubleshooting the motherboard.

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