Why didn’t Intel call the Pentium the 586? Because they added 486+100 on the first one they made and got 585.999999987.

Amusing joke, but it actually is effectively called the 586 because the internal name is P5 and Penta from which Pentium is derived is 5.[1]

Incidentally, Pentium M to Intel Core through 16th gen Lunarrow Lake all identify as P6 ("Family 6") for 686 because they are all based off of the Pentium 3.

[1]: https://en.wikipedia.org/wiki/Pentium_(original)

You’re missing the fact that Intel wanted to differentiate itself from the growing IA-32 clone chips from AMD and Cyrix. 586 couldn’t be trademarked, but Pentium could.

Also, as per the page:

> Intel used the Pentium name instead of 586, because in 1991, it had lost a trademark dispute over the "386" trademark, when a judge ruled that the number was generic.

The main reason is that it’s impossible to trademark a model number.

Also, Weird Al would not have been able to make a song, “It’s All About the 586es.” It just doesn’t scan.