[LAU] Intel Rate Matching Hub and USB soundcards
clemens at ladisch.de
Sun Jun 13 13:24:40 UTC 2010
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.
| • 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
| Workaround: None.
| Status: Fixed
(that is, fixed in chip revision B3)
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