That computer is part of a control for the electromagnetic train. By hacking all the terminals along the train tracks I should be able to reverse their polarity... thereby turning the train into a giant projectile. Without question its impact on the prison walls should create a hole large enough for Sly to escape through.
― Bentley, planning how he's going to break Sly out of "The Hole"[src]
After discovering that The Contessa is holding Sly in "The Hole," Bentley decides to help him escape. He notices a computer next to some train tracks that run near the safe house, and that it is one computer in a series that controls the electromagnetic train. By hacking all six computers, Bentley will be able to reverse the polarity of the train tracks, essentially turning the train into a giant projectile. Smashing it into the prison wall will definitely create a hole big enough for Sly to escape through.
Bentley proceeds down the track, hacking terminal after terminal. After the fifth is hacked, Bentley notes that the train is now at full speed, and that hacking the sixth terminal will reverse the tracks' polarity. He hacks the sixth terminal, and the train is sent skyward before crashing into the prison wall, opening up a large hole.