I'm only guessing, but I suspect you were born after 1980. Let's look at some highlights from 1979 (Source).
CompuServe became the first commercial online service offering a dial-up connection to anyone on September 24, 1979.
The first commercial version of SQL (Structured Query Language) was introduced in 1979 by Oracle.
Atari introduced a coin-operated version of Asteroids in 1979.
Usenet was first started in 1979.
Robert Williams of Michigan became the first human to be killed by a robot at the Ford Motors company on January 25, 1979. Resulting in a 10 million dollar lawsuit.
Bjarne Stroustrup, a Danish computer scientist, begins work on the programming language "C with classes" that will later be renamed C++.
By 1979, the TRS-80 offered users the largest selection of software available for a consumer microcomputer system. (If you have never used a TRS-80, you need to hunt down an antique and use it to really understand the overwhelming nature of this one historical fact.)
The Intel 8088 was released on June 1, 1979.
Hayes markets its first modem that becomes the industry standard for modems.
The Motorola 68000, a 16/32-bit processor is released and is later chosen as the processor for the Apple Macintosh and Amiga computers.
IBM introduces the first disk drive to feature thin-film inductive heads and an RLL (run-length limited) coding scheme (IBM 3370).
IBM announces the 4300 processor, featuring multilayer ceramic packaging and 64 Kb memory chips for the densest packaging of memory and logic circuits in intermediate-sized IBM systems. (Compared to commercial-grade CPUs in the 2020s, what IBM did in 1979 was invent a digital version of the abacus.)
First of all, you didn't clearly define what you mean by "Artificial Intelligence." That's a problem because right now "AI" is following the trend of identifying products as "green" or having the letter "X" in their names. It's being slapped on anything and everything whether or not "artificial intelligence" is involved at all. It's the latest "the world is coming to an end!" hot potato that everyone's talking about but nobody actually understands.
Ignoring fiction (and that's mandatory to answer your question), the beginnings of "artificial intelligence" stretch clear back to 1940. But you need to understand what that means. Scientists were thinking about models of intelligent, self-learning activity that would let them physically create it. (Source)
And here it is, 2023, and we have not reached that goal.
We're getting there, but there isn't "artificial intelligence" on the planet yet. Programs like ChatGPT are little more than very efficient data aggregators. They "learn" from the perspective of improving the efficiency of their core goals — but they're not thinking for themselves in any sense of the concept. (I'd give my left big toe to see ChatGPT truly embarrassed by the quality of what it spits out.)
So, what's a "powerful AI?"
I'm going to assume you're thinking of the science-fiction version of "powerful AI" and not the real-life version of "powerful AI" like automation with feedback analysis or a ChatGPT database analyzer. If that's what we're looking for, you can't have in the 1970s what we don't have in the 2020s.
If you scale that back to, for example, automation with feedback analysis, then please note the death of the first human by a robot at Ford. You already had that kind of "artificial intelligence" in the 1970s.
I'm assuming you want the former more than the later, so I continue to assert that it's impossible.
What are you lacking?
A massive world-spanning database containing vast amounts of human knowledge. Remember, the first commercial version of SQL was introduced by Oracle in 1979. It could not do what databases do today.
Multi-core computational arrays operating with gigahertz clock frequencies. (In the 1970s the max clock frequency was +/- 16 Mhz and the backplane was a LOT slower than that.)
Dense high-volume, very fast RAM.
Exabytes of storage — possibly Zettabytes of storage — worldwide.
Keep in mind...
- Laserdiscs were introduced to the market in 1978.
- Seagate introduced the first hard drive for home computers in 1980. It was 5 megabytes.
- The first terrabyte hard drive didn't hit the market until 2009. (Source)
- Finally, a world-spanning reasonably fast network (separate from the database of #1). The Internet as you recognize it fundamentally didn't exist prior to 1983 when TCP/IP was introduced. There was no world-spanning Internet in the 1970s. There were modem-accessed bulletin board systems1 (BBS, I actually miss some of those early BBS sites), but that's like claiming you have a Ferrari when what you really have is a 2-cycle lawn mower go-kart. And that might have been a very generous comparison.
Thanks for the walk down memory lane, but does it matter?
Having said all that, none of it matters! Authors today are really stuck on the idea that things must be entirely "realistic." Baloney! Just because you can't produce the schematics for the computer that operates your AI or the software that instantiates it using 1970s tech doesn't mean you can't have it.
The idea of machines that could intelligently take over the world began with E.M. Forster's story "The Machine Stops" in 1909. They by no means had the technology to produce the omnipotent machine of the story (we still don't over a century later) — but the story is an absolute sci-fi classic.
So, after having told you that technologically it's impossible, I want you to confidently present with absolute assurance that you can succeed a magnificent vulgar hand gesture and go write that story.
If I wanted fiction based on realism, I'd read the biographies of politicians.
But I do recommend that you take the time to specifically define what you mean by "artificial intelligence." Rationalizing the tech in your world would be a lot easier if we knew exactly what you wanted to achieve. And remember that there are ways to creatively solve the problem without depending on "Real Life" technologies. Go watch the Star Trek TOS episode "Spock's Brain."
1 To be fair, the ARPANET existed in the 1970s. It connected whole dozens of computers at different locations in the U.S. using, primarily, phone-based MODEMS. In other words, it existed, but it wasn't on all the time... and dozens of sites don't make the Internet, if you know what I mean. The technology was emerging, but hardly capable of creating Colossus.