AMD Ethernet Controller Problem

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Receive descriptor incrementing of Am79c973 (PCNet FAST) Ethernet controller

I would like to understand the behavior of the Am79c973 Ethernet controller,
when it does not own the current Rx buffer. According to the manual it polls
the descriptor of this and the next buffer (why does it check the next
buffer too?) and it should wait until the first descriptor is owned by the
controller.

However under heavy Ethernet load I experience a different behavior: it
seems as if it can skip to the next buffer and continues there, this causes
the driver to hang at the skipped buffer when it arrives there since it is
owned by the controller. It will however not get stuck there for ever: after
having received 64 (size of RxRing) packets the controller must have done
and completed a scan of the Rx ring and writes the single remaining packet
belonging to it.

Btw: RxPoll is enabled, SW-Style = 3, LAPP disabled

Thanks for your help,



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