Gigabyte MA78GM-S2H questions

Discussion in 'Gigabyte' started by GTS, Jun 9, 2008.

  1. GTS

    GTS Guest

    Been years since I had a gigabyte board, but very impressed with this one.
    Using it in a HTPC, which it is ideal for.
    Q1 Front panel audio header. My case
    seems to have AC-97 front panel audio (although Coolermaster state HD audio,
    the leaflet with the case says AC-97). I disabled the front panel jack
    detection, as it did not work, and the sound now works fine from the front
    panel. But oddly it comes out from the back motherboard audio jack at the
    same time. The manual says that when using AC-97, you can only have front or
    back, not both, and that is what I wanted - the sound cutting off when you
    plug in headphones. As it is, I have to manually turn down the sound on my
    TV each time I want to use headphones. which is a bit of a pain. Either the
    manual is wrong or my case wiring is unusual? I wondered how it works for
    other users...
    Q2 The Gigabyte SB700 heatsink on the board gets very hot in use. None of
    the software supplied seems to give me the temperature, just the usual CPU,
    system and hard drive temps. Should I be worried about the heat of this
    GTS, Jun 9, 2008
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  2. GTS

    Paul Guest

    On the original AC'97, rear speaker muting is implemented via
    the way things are wired. The 2x5 F_AUDIO header in those
    days, had stereo headphone output signals, but also had two return
    signals. By means of switches inside the headphone jack on
    the computer case, plugging in front headphones, interrupted
    the return signal flow, which caused the rear speakers to be
    muted. It meant there was a relationship between the
    headphones in the front, and the speakers in the back.
    If you didn't have F_AUDIO wiring connected, two jumpers were
    put in place on the 2x5 header, to maintain signal continuity,
    so the rear green jack would work.

    With HD_Audio, things are different. Firstly, there are enough
    outputs on an HDAudio CODEC, that front headphones and rear
    speakers have separate ports. When muting is desired, it is
    implemented in the driver software.

    HD_Audio has two plug detection methods. One method is based
    on switches inside each jack. When you plug in a 1/8" plug,
    the switch is activated, and via the wiring to the CODEC,
    the CODEC knows there is a state change underway.

    Most computer cases, lack the special jacks with the switch
    inside them. As a result, a second fallback method is used.
    Many CODECs have impedance sensing, were (presumably) a measurement
    is done on a regular basis, looking for current flow. Based on that
    measurement method, the driver and control panel know when
    something has been plugged in. (The measurement method is
    not documented, so remains a mystery. Presumably someone has
    a patent on it.)

    Now, in theory, it should be easy, when headphones are plugged in,
    to mute the rear green jack. The problem is the complexity of the
    RealTek control panels, and figuring out what you need to do
    to get that behavior. RealTek supports multistreaming, meaning
    you can send separate audio content to front panel and rear speakers.
    And you don't want that. I think it is also possible to support
    more than one set of headphones at a time, via the chip (each port
    can have the headphone amp enabled on it). There is plenty of
    functionality there, but looking at this page, I cannot see a
    specific tick box that does "old style" muting in software.

    I wish RealTek would write a manual like that, to make it all
    easier to figure out.

    Paul, Jun 10, 2008
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  3. GTS

    GTS Guest

    Thank you for excellent info.
    Having read through the guide you linked to, I am confident my Realtek audio
    is setup correctly for AC97 audio - I don't have multi-streaming enabled,
    and turning on front panel jack detection simply means that I loose audio
    from the front, as it never detects the headphones being plugged in. Looking
    again at the motherboard manual, it states that pin 10 and pin 6 are not
    connected. But my case FP audio connector has pin 10 as L RET and six as R
    RET. If these act like the old jumpers you used to get on the motherboard,
    then I guess that is one explanation why the sound is coming from front and
    back at the same time. Odd though if the mobo manual says 6 & 10 are not
    I could try disconnecting 6 & 10 from the front panel audio plug, but what I
    don't want is a situation like my last case, as if you plugged in the front
    audio connector on that one, the rear output was permanently cut off - the
    only way to get the rear output working was to disconnect the FP header. On
    that case, the problem was that there was no L RET or R RET wires. The HD
    audio panel is confusing - I'm now not even sure if it is meant to detect
    headphones in AC97 mode or not!
    GTS, Jun 10, 2008
  4. GTS

    Paul Guest

    In principle, you shouldn't connect L_RET and R_RET, because if you do,
    they go to the jack detection wiring. That means the audio gets wired
    to the jack detection resistor tree, placing a small DC connection on the
    front headphone jack. So start by disconnecting them, if possible. I
    don't think that will affect anything in a positive way, but they
    aren't needed, and neither should jumper plugs be needed if
    the audio header is not being used. Since HDaudio has separate ports,
    there is no reason to "return" the front audio signals to anything.

    In general, for all the AC'97 computer cases out there, and HDaudio
    equipped motherboards, only five wires are required. Two for
    headphone contacts tip and ring, two for microphone contacts
    tip and ring, and a common ground for both. Since an AC'97 computer
    case doesn't support jack sense via separate side switches, there
    are no other useful wires to connect up.

    Once you've done that, go back and play with the jack detection setting,
    and see if any behaviors have changed.

    Paul, Jun 10, 2008
  5. I wouldnt worry to much on the Southbridge chip. I've had mine running hot
    for about a year now, and it runs fine. You can do a bit of modding and
    maybe put some Compound to reduce the heat, and there are SB fans etc you
    can get for very cheap. It shouldnt really matter that much though.
    Stephen Parnicky, Jun 11, 2008
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