Main Computer Upgrade: LAER Mod "Auxiliary Recharger Chip"
It can be found in the Big MT west tunnel. Heading down along the entrance, take a right at the first opportunity this room has several protectron and the The Custodian, then go straight through the hallway ahead with the red light. The upgrade is on a shelf on the left wedged between a duffle bag and the side of the shelf.
This holotape contains an upgrade file for the Sink robotic assistant: "Central Intelligence Unit."