HI. i was thinking about random stuf

And i was wondering when you connect router to router , people use serial cable and usually set the clock at 64000. thats 64mB/s right?
but if i connected my router with 10/100 ethernet (interface ethernet 0/0) with another router's ethernet interface should i run 100mB at full duplex?
wouldnt that supply a faster data rate??
also can routers perform in full duplex. because to my understand full duplex can be achieved b Switch-Switch Switch-Host and Host- Host using a crossover cable. Can routers be setup with a cross over cable to run full duplex at 100mB/s?
just wondering if people setup their router connection by ethernet instead of serial. and would that supply a faster data transfer rate??
sorry for the newb question