Completion of the Mission: Countdown quest requires a total of 15 undamaged mainframe cores. One of the way to satisfy that requirement is by collecting damaged mainframe cores from the computer consoles in the lower level of Site Alpha, Site Bravo, and Site Charlie, and then repairing them at a tinker's workbench.
A damaged mainframe core can be repaired for use in the Mission: Countdown quest:
Damaged mainframe core (1)
Mainframe core (1)
Prior to patch 220.127.116.11, damaged mainframes cores had a weight of 0.