I vaguely remember that at least one version of the 6502 had half a mul instruction, that is, an attempt was made to add one, but it was buggy: it only worked for some multiplicands (ones without any neighboring one bits or something like that). That made for interesting programs, where, depending on the arguments one would compute a times b, b times a, a1 times b plus a2 times b for some a1 a2

6809 did 8x8 mul.

6809 was one of the first to have a mul instruction, and was used in the initial development of the macintosh: http://www.folklore.org/StoryView.py?story=Good_Earth.txt

Awesome! In 11 clock cycle (not counting the set-up, i.e. loading the hardcoded source registers with the desired values).

That's interesting, thanks, I remember writing my own on the Z80.