Hi. I'm trying to figure out who played the Emperor in the different movies, originals and SE etc.

I looked on IMDB and found the following:

Star Wars (Ep 4): no entry for Emperor
ESB: Clive Revill but only as the voice. Well if he was the voice who was the human?!
ROTJ: Ian McDiarmid Really?!?!?! Or was that one of the edits?

I don't need to list for Ep1 and 2 cause we know it was Ian McDiarmid.
I'm just wondering if Ian was the actor who played the emperor in Eps 4 and 5 and was it really him in 6?!

Thanks!