[LAU] Intel Rate Matching Hub and USB soundcards

[Jeremy Jongepier]

On 06/13/2010 03:24 PM, Clemens Ladisch wrote:
> Jeremy Jongepier wrote:
>> Does anybody know if there is any relationship between the Intel Rate
>> Matching Hub and poor performance of USB soundcards?
> 
> The "Rate Matching" behaves just like a normal USB hub; this design
> choice does not introduce any problems by itself.
> 
> However, the USB controllers in these chipsets (5 and 3400 series) are
> just plain buggy; the bug list ("specification update") says:
> | 6. Intel® 5 Series Chipset and Intel® 3400 Series Chipset Full-Speed
> |    USB Isochronous Packet Truncation
> | 
> | Problem: Full-Speed isochronous-out transactions with multi-frame
> | packets may be truncated, in the presence of Full or Low-Speed USB
> | asynchronous transactions.
> | • For this to occur, two devices, one performing Full-Speed
> |   isochronous-out transactions and one performing asynchronous
> |   transactions must be connected to the same USB controller
> |   (Ports 0-7 and 8-13).
> | 
> | Implication: In the case of a USB audio device this issue may result
> | in no audible impact or audible artifacts such as pops and clicks.
> | 
> | Note:
> | • High-Speed and Low-Speed USB devices are not impacted by this issue.
> | • Only devices supporting Full-Speed isochronous-out transactions that
> |   Intel is aware of are audio devices, such as sound adapters,
> |   speakers, and headphones.
> | • Intel has only observed the issue when a Full-Speed audio devices
> |   and Full-Speed USB web camera are connected to the same USB
> |   controller.
> | 
> | Workaround: None.
> | Status: Fixed
> 
> (that is, fixed in chip revision B3)
> 
> 
> Regards,
> Clemens

Hello Clemens,

Thanks for the info! That's a real bummer for those who acquired a
machine with these chipsets and want to use it with a USB soundcard :(
Case closed, thanks again.

Best,

Jeremy