Well if we're considering alternate histories where a civilization gains access to a working computer then it's basically impossible to tell. It depends on so many variable factors. Whether someone in that time period takes a significant enough interest to even look into it in the first place, whether they're smart enough to solve the question of what it's doing, and even who's hands the computer falls into.

There's a famous example of an ancient Roman trinket that was kept in the collection of a wealthy person. It was a small device that when placed over hot water would spin. We would recognize that device today as a steam turbine and we would know that it has the possibility of sparking the industrial revolution if the right person got a chance to look at it.

So if an ancient civilization got their hands on a modern computer and managed to do anything useful at all with it, it would alter world history in ways that we wouldn't recognize it anymore. Even if they didn't directly reverse engineer the computer but instead gained insight into other technologies like electricity or plastic production, it would alter world history in such a way that the modern computer would almost certainly be produced much earlier than in our own history which kind of nullifies the point of the question.