4 Full speed isochronous->1 High speed isochronous = 100% CPU

Discussion in 'Windows Vista Drivers' started by lugeon, Sep 7, 2006.

  1. lugeon

    lugeon Guest

    We are using 4 USB audio device (PCM2902, manufacturer TI) connected to the
    Southbridge ( 82801 GB/GR, Manufacturer Intel, a.k.a. ICH7) of a motherboard
    through a Multi-TT high speed USB Hub (2507, manufacturer SMSC).

    It means that there are four periodical isochronous full-speed streams that
    are converted to one High-speed USB stream by the Hub, before being sent to
    EHCI controller of the Southbridge.

    Software configuration is Windows XP (Professional) SP2 with auto-update
    activated. (Kernel Version 5.1.2600.2180)

    In this configuration, there is a high increase of CPU load (peak to 100%)
    when audio channels are all activated in both direction (Wave In, Wave Out).

    It induced lost of many audio frame and lost of audio stream.

    Another interesting test has been done connecting directly the four USB
    audio devices directly to Southbridge UHCI controller (i.e. using 4
    full-speed USB stream).

    In this case, it operates correctly (less than 20% CPU load without lost of
    audio frame), what validated our software.

    Is it a way to use the USB Hub in High speed mode without having the CPU
    reaching 100%?


    lugeon, Sep 7, 2006
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