AAAHHH... I have the 8391 which is used for interfacing with CAT5... the data sheet refference is for the 83910 which is pin compattible with the one I have. The rubb is interfacing from the 8390 to the 8051... this is the most important part for me.

I will be using Cat5 which is done with the 8391 (or 83910) for ten base ether.. I also have the magnetics to do the job. Coax is out of the question because my ethernet switch is cat5, and with 128 ports I think it is big enough to handle everything else...
I would send you a diagram but as you know it cant be put here... at least I havent figured it out.

Hope this helps... Thanks