Does anyone know how to set up a direct ethernet link between my iMAC and my (Ubuntu) linux box?

What I am after is a direct connection to my Desktop so that I can access my Samba shares at a decent bit-rate, as near to 100Mb/s as possible, and in turn transfer all of my files accross to the MAC.

Currently, going through my router, the transfer rate is around 350-400Kb/s. This means transfering my 250GB of data across is going to take many days...

FYI - I do have a known good cable between the two boxes. The Desktop NIC supports 10/100 and is set to 100 AFAIK.

Help appreciated,