Asus P5GDC Deluxe ships with defective C-Media audio chip

Discussion in 'Computer Support' started by Frank, Dec 29, 2004.

  1. Frank

    Frank Guest

    I have spent over 5 hours with Asus tech "support" trying to get a
    microphone -- any microphone -- to function with a P5GDC Deluxe
    motherboard. The answer from tech support is that It won't at any
    level that is usable.

    The problem is the C-Media chipset on this MB "does not support" a
    20dB microphone boost (It took them 5 hours to come up with that
    answer). That means that every microphone I am familiar with won't
    work (including a $200 Sennheiser 845 S).

    The board is designed for gaming with a PCI Express 16X AGP, yet they
    screwed up the audio.

    Asus has always been high on my list (I have bought many of their MB's
    and have recommended them to others as well. No more.

    Anybody else have a similar experience?
     
    Frank, Dec 29, 2004
    #1
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  2. Does ANY conglomerate have a decent sound driver that does what it is
    supposed to do or are they just releasing buggy code that is a
    nightmare, for the profit? Oh yeah, this IS about money....;o(

    ....just five hours?! I may not want to recommend Asus again. The
    last five or so computers that have hit my workbench had trouble with
    the sound drivers....the original sound drivers that came with the
    "Recovery Disk". One of them happened to be a C-Media chip. After
    much stress and expletives, I finally tamed the darn thing....but it
    WAS NOT fun!!!
     
    @}-}-------Rosee, Jan 5, 2005
    #2
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  3. Frank

    NoMoreAsus Guest

    The problem seems to be Asus using C-Media, which "conforms to" the
    Intel HDAudio ("Azalia") that Intel is pushing to replace the current
    AC97 standard. I guess the answer is to stay away from any board
    using the C-Media chip set and/or the Intel HDAudio spec.

    The more I think about it, why not stay away fronm Intel, period
    (Hello AMD!)? <g>

    If you want more details, the Intel HDAudio spec is here. There is no
    mic boost in the spec.

    ftp://download.intel.com/standards/hdaudio/pdf/HDAudio_03.pdf

    See "7.3.4.10 Amplifier Capabilities" on page 162, for how gain
    is specified.

    The CMedia datasheet for the 9880 chip is here. Section 5.4.5 on
    page 22 lists input amp capabilities, using terminology from the
    Intel spec:
    http://www.cmedia.com.tw/doc/C-Media CMI9880 Datasheet rev 0.99C.pdf

    StepSize = 05h ==> 1.5dB steps
    NumSteps = 1Fh ==> 32 steps
    Offset = 00h ==> implies no attenuation capability - likely wrong!

    Taken at face value, this says the max gain setting is +46.5dB.

    If we compare this to a typical AC97 spec, like a Realtek ALC650,
    that chip has -34.5dB to +12dB, in 1.5dB steps. And, it has a
    microphone boost, for an additional 20dB. That means the Realtek
    ALC650 spans -34.5dB to +32dB gain.

    So, if we believed the CMI encoding for their gain capabilities,
    the gain setting would have more than enough gain for a microphone
    (i.e. +46.5dB, as the offset is zero). But, instead, I think the
    CMI "Offset" value should be a non-zero value, as it is unlikely
    the CMI9880 gain block is all gain - it likely has a range more
    like a traditional AC97 chip (i.e. -34.5 to +12dB). To emulate
    the mic boost, CMI should have designed the chip to use more
    than 32 steps.

    It would suggest this is a problem with the CMI implementation
    of the Azalia spec, and either the Cmedia control panel is
    being confused by the "Offset = 00h" value, or the chip really
    only does -34.5dB to +12dB and doesn't have enough gain for anything
    other than some kind of amplified microphone (like maybe an
    electret mic ?).

    Notice how C-Media's web form doesn't even admit to a CMI9880 chip:

    http://www.cmedia.com.tw/etech-re2.asp
     
    NoMoreAsus, Jan 15, 2005
    #3
  4. Hmmmm....seems I've already read a shortened version of this *.pdf
    document. Thank you very much for drawing my attention to the
    complete version.

    I don't remember the *EXACT* details, but I do remember, on every
    shutdown and restart of the computer, there was this terrible
    "honk/squeal/grunt" as it loaded the sound drivers. I had already
    disabled the Windows sounds, but that honk was horrible. I tried EVERY
    version of driver. I was fast beginning to hate that C-Media chip.

    <schnippen>
     
    @}-}-------Rosee, Jan 27, 2005
    #4
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