The Jupiter 50/80 does not have a drum machine on board. It has a drum layer where you can manually play rhythms and possible record them for playback. Also there are one or two sounds that are similar to the TR-808/909 but again they have to be played manually (or via the arpeggiator).
I guess you could record a pattern on a DAW and save it as an SMF and import it into the arp but that's as close as you're going to get - which is light years away of what you want!
Thanks. I would love a TR-8! However, I just bought the J-50, and am still paying that off. Plus I have an Alesis SR-16, that I bought used a few years back. I guess I could trade that in, but I probably would'nt get much for it...