Hi,
I would like to ask how the port register works on the 101? I guess it is not the same as on the Uno, or is it? I couldn’t find any documentation for it. 
I'm wondering the same thing, so I'm going to follow your thread. 
I did find some things by mucking around in wiring_digital.c, rather than repost it, here's a link to the thread: Direct Port Manipulation, Arduino 101. Incomplete pins_arduino.h? - Programming Questions - Arduino Forum
Nothing working yet though