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,