Certified IT Support Professional Learning Resources Troubleshoot CPU and Motherboard

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Troubleshoot CPU and Motherboard

Dark Screen
Check that the computer has power if you have a dark screen. No video can indicate a larger issue, but often power can be the main cause. Make sure all of the power cables are plugged in and that the battery is charged if your system is a laptop and no power supply is available. Most computers have a power indicator light. If this light is not on, you may have a power issue. If you are receiving power but still have a dark screen, check that the monitor is plugged in if you are using a desktop computer. If it is plugged in, or if you are using a laptop, you need to check the graphics card. Refer to your system's user manual to find out whether the video card is attached to your motherboard. If it is, as is generally the case with laptops, you may find that a graphics card failure means getting a new motherboard. Otherwise, try to find a compatible graphics card and plug it in. If you get video, the graphics card is the issue and should be replaced. When using a laptop, plug in an external monitor and see if you get any video. If you do, the laptop screen may be the issue; if not, the motherboard or the CPU may need to be replaced.

Beeping from your machine may indicate that the RAM has been knocked out of place or that one of the modules is faulty. Check in your owner's manual whether your machine requires you to install your RAM in pairs. On Intel Core Duo machines, this is required for best performance. Turn off your computer and remove any components that block the RAM. On most laptops, the RAM can be accessed by lifting up the keyboard or removing a small door on the bottom of the machine. On desktops, the access panel will need to be taken off. Access the RAM of your computer, take it out and reinstall it. Turn on your computer and listen for beeps. If the beeps are still present, replace the RAM with a new module. If the RAM needs to be installed in pairs, try one piece of the old RAM with one piece of new RAM to isolate which one is faulty. If after replacing both pieces of RAM the machine still beeps, you may have a RAM slot issue, meaning you need to replace the motherboard.

Reseating CPU
If you are experiencing video issues, you may need to reseat the CPU. Open up your computer and check to see if the CPU is lying flat. If it is not, lift it up and reseat it. Usually the CPU is attached to the heat sink, so take care when lifting it up so as not to separate the two. Check to see whether the computer gives you video. If it does not, you may need to reset the computer's motherboard to its default settings. Each motherboard is reset differently. Look up the make and model number of the motherboard to find out reset procedures.


Some number of short beeps that are sounded by the BIOS upon startup when a memory, cache or processor error is encountered. There are numerous beep code patterns, and Phoenix BIOS codes are long and short beeps delivered in groups. The following beep codes are for AMI BIOSs. There are additional beep codes for this BIOS not included here.

1 Beep - Refresh Failure
Reseat/replace memory, troubleshoot motherboard.

2 Beeps - Parity Error
Reseat/replace memory, troubleshoot motherboard.

3 Beeps - Memory Error (first 64KB)
Reseat/replace memory.

4 Beeps - Timer Failure
Troubleshoot motherboard.

5 Beeps - Processor Failure
Troubleshoot CPU, motherboard.

6 Beeps - Keyboard Controller Failure
Troubleshoot keyboard, motherboard.

7 Beeps - Virtual Mode Exception Error
Troubleshoot CPU, motherboard.

8 Beeps - Display Memory Failure
Trouleshoot display adapter, motherboard.

9 Beeps - ROM BIOS Checksum Failure
Replace ROM BIOS, troubleshoot motherboard.

10 Beeps - CMOS Shutdown Register Failure
Troubleshoot motherboard.

11 Beeps - L2 Cache Failure
Troubleshoot L2 cache, motherboard.

Continuous Beeps - Memory or Video Failure
Troubleshoot memory, display adapter, motherboard.



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