Another one that we oddly hadn't seen until now: Colossus: The Forbin Project (1970). I was expecting a 50s drive-in SF feature, but it was something else. I must have been thinking of GOG.
It starts with ranks and ranks of computer equipment, long halls lined with it. A scientist, who turns out to be Forbin (Eric Braeden), is locking it down behind a bank vault, then crossing a bottomless radioactive chasm on a retractable bridge, and finally another vault door. The chasm is a standard feature of all advanced designs, from Forbidden Planet on through Star Wars.
When Forbin is ready, the President (Gordon Pinsent) announces that this computer, Colossus, is now in control of all US nuclear forces, and completely autonomous - down to a nuclear power plant so you can't just pull the plug. Almost instantly, Colossus announces that the Russians have their own machine, and that they are communicating. When Forbin and the President try to disconnect them, all hell breaks loose.
The pace of the movie is interesting - there is no build up, no discussion of the wisdom or morality of turning the security of the world over to an omnipotent computer. Gordon Pinsent, who looks like a blander John F. Kennedy (Braeden refers to his character as "President Kennedy" in an interview), is just glad to have the nuclear responsibility taken from him. Forbin just believes in rationality, logic, and the chance to meet a new kind of mind. It also lets us get to the fun part earlier - the man vs. machine struggle.
To evade Colossus' ever-present surveillance, he convinces Colossus that he needs private time with his mistress - fellow scientist Susan Clark. So every night, they strip naked and go to bed to plot in secret. This gives us a few cute scenes of the naked-actor-with-naughty-bits-blocked-by-random-upstage-props. In this case, a wineglass in front of Clark de-magnifies her breasts, giving her a tiny top. The dregs of the wine in the same glass protects us from the view of Braeder's manliness, unless that's the tip poking out beneath the glass?
In conclusion, very cool high-gloss early 70s SF.