A7N8X - Gainward 6800GT sound and video distortion

Discussion in 'Asus' started by No-one, Sep 9, 2005.

  1. No-one

    No-one Guest

    Hello,

    I have recently put a Gainward 6800GT card in an A7N8X v.106
    motherboard. I am now noticing crackles on the audio, both with the
    onboard sound and a Soundblaster lie card I swopped in. In addition,
    the video peridicaaly breaks up in places on the screen. With a
    digital TV unit, while the audio starts fine in play mode, switching
    to record produces the above errors plus the picture "lags" every few
    seconds (like a brake was applied).

    Is this likely to be a result of this cards interaction with this
    motherboard? I am going to swop in another make to test it but I am
    rather peeved to say the least if this proves to be the case.

    TIA
     
    No-one, Sep 9, 2005
    #1
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  2. No-one

    Paul Guest

    I've seen a couple of suggestions for fixing stuff like this.
    One was to disable APIC on Nforce2. Another is to play with the
    PCI Latency settings on the various bus masters. The PCI Latency
    setting can be programmed with Powerstrip from entechtaiwan.com,
    or this tool "PCI Latency 2.x" was suggested.

    http://downloads.guru3d.com/download.php?det=951

    There is another setting which would help on other boards, and that
    is "Delayed Transaction" [Enabled]. That allows a transaction to
    a slow-to-respond device to be temporarily "parked", while other
    fast transactions continue to occur. On some chipsets, accesses
    to devices in the Southbridge, tie up the PCI bus until the answer
    comes back. Enabling "Delayed Transaction" allows the bus to
    be released, and the Southbridge operation retried after a short
    interval. The end result is better bus efficiency, sometimes
    enough to stop audio crackling.

    But, on the Nforce2, the feature "Concurrent PCI" implies that
    Delayed Transaction is always enabled. So there is no corresponding
    BIOS setting. You should already be receiving whatever benefits
    that optimization can provide.

    From manual e1170 for A7N8X:

    "Concurrent PCI
    Concurrent PCI maximizes system performance with simultaneous
    CPU, PCI and ISA bus activities. It includes multi-transaction
    timing, enhanced write performance, a passive release mechanism
    and support for PCI 2.1 compliant delayed transactions. Concurrent
    PCI provides increased bandwidth, reduced system latencies,
    improves video and audio performance, and improves processing
    of host based applications."

    When I look through some Intel datasheets, I see many pieces of
    hardware have Latency registers. Some of the registers are fake
    (hardwired to 0x00, function only as scratchpad registers etc),
    while others are real. Generally what I find, is an eight bit
    register, where the upper five bits are writable. The max value
    is 0xF8 and the min value is 0x00. 0xF8 corresponds to 248 cycles.

    The bus latency value, is the maximum time a bus master can
    occupy the bus, until releasing the bus to another master.
    Now, architecturally, not all hardware devices in your computer
    sit on the exact same bus, but it is possible for a "bus hog",
    no matter where it is located, to have an impact on other
    devices. If a device somewhere grabs the bus, and does a 248
    cycle long data burst, that is time that other cards will not
    be able to get/put any data they've got.

    Video cards are generally set quite high. Expect to find 248
    for them. Dropping the video card allocation can sometimes
    make the machine smoother, at the expense of perhaps dropping
    the benchmark for the videocard (i.e. adjust max latency,
    rerun 3DMark and see what you are losing).

    The BIOS has a PCI Latency Timer setting, and it will generally be
    set to 32. I don't know whether the BIOS writes this value
    into all the cards, or the PCI Latency setting is being
    applied to a single register somewhere in the chipset.

    http://www.rojakpot.com/showFreeBOG.aspx?Lang=0&bogno=138

    The deal with any max latency register is, the higher one of
    these is set, the greater the percentage of bandwidth the
    card can grab. But, a card which has a real time requirement,
    like a sound card, can be starved waiting for data, if some
    other card(s) are too greedy. Rather than custom tune every
    system, that is why settings like 32 are generally used, as
    a compromise between monster benchmarks for individual hardware
    devices, versus smooth overall computer operation. You may
    find tweaking is nothing but a PITA, and not a permanent
    fix.

    Also, you didn't mention the brand/model of your "digital
    TV" unit, but be aware that when these record, they
    create double the bus traffic. The data is being recorded, but
    the data is also decompressed and sent to the frame buffer
    at the same time. In some cases, the video card is even
    being used to do IDCT (inverse discrete cosine transform)
    as part of the decompression process. Both the processor
    in the computer, and the system busses, can be pretty busy
    when this happens. It might help a bit, to drop the size
    of the monitoring window down a notch, to reduce the amount
    of decompression generated traffic.

    So, have a look at your PCI Latency register settings, and
    see if cards other than the video card, have been given
    a very high setting.

    HTH,
    Paul
     
    Paul, Sep 9, 2005
    #2
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  3. No-one

    No-one Guest

    [snip]

    Thanks for the suggestions. I am also experiencing the same problem
    with a BFGTech 6800GT I swopped in. (Changed drivers as well)

    What gets me is that everything was working perfectly until a couple
    of days back.

    Best regards.
     
    No-one, Sep 9, 2005
    #3
  4. No-one

    No-one Guest

    I nuked the partition, reinstalled and this appears to have cleared a
    number of problems.

    Regards.
     
    No-one, Sep 10, 2005
    #4
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