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What is causing the alarm coming from my motherboard?

517 Views 8 Replies Latest reply: Nov 27, 2012 3:10 AM by japamac RSS
adaminvic Calculating status...
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Nov 17, 2012 9:54 PM



The problem that I am experiencing is a loud alarm that is coming from the motherboard. The computer is able to boot up and I can log into my user account. Typically about 10 seconds after the desktop is visible, a surprisingly loud beeping starts. The beep lasts approximately a quarter of a second, with about the same length of silence, before repeating. The computer continues to operate normally, however I turn it off for fear that there justifiable cause for the alarm going off, and it is extremely annoying.


There is also a red LED that is lit on the motherboard with the number D518 beside it. I have not been able to find a satisfactory answer for the cause. Has anyone experienced this before? Any suggestions for where to start looking for a cause and the associated solution?


It is a Powermac G4 MDD with a single 1.25 GHz processor and 756 Mb RAM, running OSX 10.5.8


Thanks in advance.

PowerMac, Mac OS X (10.5.8), G4 MDD Single 1.25 GHz, 756 MB RAM
  • BDAqua Level 10 Level 10 (114,775 points)

    HI Adam,


    Can you count the beeps or flashes?


    1 beep = no RAM installed

    2 beeps = incompatible RAM types

    3 beeps = no good banks

    4 beeps = no good boot images in the boot ROM (and/or bad sys config block)

    5 beeps = processor is not usable


    In addition to the beeps, on some computers the power LED will flash a corresponding number of times plus one. The LED will repeat the sequence after approximately a 5-second pause. The tones are only played once.


    Note: In this case, a flash is considered to be 1/4 second or 250 ms or greater in length.



    The following table lists the new tones and their meaning:


    Tone(s)          Description

    1 tone, a 5-second pause, repeat          No RAM installed

    3 successive tones, a 5-second pause, 3 successive tones          RAM does not pass data integrity check

    1 long tone when holding down the power button          Firmware upgrade in process. See About firmware updates for Intel-based Macs for more details.

    3 long tones, 3 short tones, 3 long tones          Firmware restoration from CD in process. See About the Firmware Restoration CD (Intel-based Macs) for more details.


  • japamac Level 7 Level 7 (24,390 points)

    Is a graphics card that requires addtional power (Molex connector) installed without the power connection? That will cause beeping with some, like the Geforce 7800 GS.

  • Jacumba Level 4 Level 4 (2,325 points)

    It sounds like one of the slots on the motherboard that holds the ram has failed. Try pulling the ram and moving it around.

  • BDAqua Level 10 Level 10 (114,775 points)

    WEll, see what Disk Utility says if you just try to Verify it.


    DiskWarrior might be your best option.

  • japamac Level 7 Level 7 (24,390 points)

    The RocketRAID card does have a speaker for audible alerts, and will beep when a disk or array has failed/is failing.

    You're on track with the source of the sound, I would say.


    Regarding the drive, a MyBook drive is typically a "green" drive; 5400 RPM type that spins down whenever possible to save energy.

    If the drive is a green drive, I would say that the RocketRAID card just doesn't like it, and rightfuly so. Green drives aren't what one wants for a RAID array; they are slow.


    Glad to hear that you like the new fan.

    I have tried a few different PSU fans and like them all better than the OEM fans!


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