PPC440GX ethernet oddities

[Jeff Mock]

Wolfgang Denk wrote:
> In message <456A641D.7070904 at mock.com> you wrote:
>> Here's the weird part.  On one of the four prototype boxes, if I plug
>> the second ethernet port into gigabit switch and get a link light (2nd
>> interface is not enabled under linux), the DMA behavior will change and
>> I can see the ring buffer get as large as 25MB (up from 512kB!)
>>
>> Only one of my four boxes shows this strange behavior, and only when the
>> second ethernet port is connected to an ethernet switch. Everything
> 
> Are you using exactly the same switch,  and  the  same  port  on  the
> switch, and the same network cable with all of your boxen?
> 

Yeah, I'm using the same switch, cables, and server machines for these
tests.  I've done quite a lot of fiddling with servers, cables, and
switches looking for some differential behavior, but the only thing I
find is that with second ethernet port unconnected, my ring buffer will
consistently only fill to 512kB, but with the second ethernet port
connect to get a link light (disabled under linux), the ring buffer will
get as full as 25MB over time.

jeff