The Arthur Biochip (aka Arthur-'Infected' Biochip) is a secret upgrade received with an order of cornbread ("e" key easter egg).
Found Saturn Orbit - 1.28.2247 AD
This Biochip is a latant, temporal anachronism. It's not supposed to be infected with the artificially intelligent software virus known as Arthur until the future.... when you discover him in the past... uhh.. just play the sequels later and you'll figure it out. :)