> The packet structure is the pretty much the same for 10 and 100. The type > of encoding used on the wire is different, 10Mb is manchester encoded (2 > voltage levels with some predistortion) and 100Mb is MLT3 encoded > (3 voltage > levels). But this is nothing you have to worry about the switch chip and > phy chip take care of all of that. The switch chip is your transformer > although a FIFO is probably a more accurate term. I packet is > brought in , > buffered, the preamble is rebuilt and it is routed via a lookup > table to the > correct port where it is sent out at the proper speed for that port. Do I understand correctly that the dual speed hub is converting between manchester and MLT3 encoding along with buffering the packets? This brings up another question. How big is the buffer and what happens when it fills up? I'm guessing there is some sort of flow control built in to keep things sane. Hopefully they didn't use ctrl-s and ctrl-q! Ha ha! Mike