On 20:47:57 Nov 29, Stuart Henderson wrote: > Been there, done that. If you use plaintext protocols (ftp or so) > over the interface, you'll see random corruption visible in the > data (e.g. directory listings). > > At 133MHz there's some corruption between motherboard and card. > Disappears at 66MHz. > > Normally this would be masked by TCP checksums (you'd get packet > loss, but it would mostly be corrected rather than pass corrupt > packets up the stack), but the em(4) does offload TCP checksum > processing to the card, so the checksum no longer covers the > transfer over the PCI bus, hence the wierd protocol errors.
TCP checksums or for that matter any checksum cannot catch *all* errors. The best way to consistently reproduce that is by using our own scp(1). Since there is a MAC computation for every packet, this will easily help you identify the problem. If you do a recursive transfer and play with large files, it gives you enough headroom to track down the bug(s). Best of luck. -Girish
