Ethernet problem turned out to be a memory / DMA problem

Thank you very much but I just managed to solve my problem and get bidirectional ethernet communication for the first time after nearly a month of working on it.

Turns out to be a memory timing problem after all even though the Eclipse memory test project showed no errors.

Turns out that the original phase lead / lag calculations for our SDRAM was done incorrectly. But the interesting thing was it was close enough that normal processor access works just fine but only the DMA transfers from the Ethernet stack were corrupted.

I had initially ruled out RAM as a source of my problems because it passed all processor based RAM checks. In hindsight that was a mistake. Changing the phase shift of my SDRAM clock from -3 nS to -1.5nS solved the problem.

Thanks again, I have learned a lot troubleshooting this problem.

David