The Oberheim OB-X is a polyphonic analogue synthesiser. It was used by Prince on Dirty Mind and Controversy. The main riff to When You Were Mine was played on an OB-X. The OB-X probably appeared on 1999 and Purple Rain too, and it was in use as late as 1984 on "Manic Monday". It was also used live by Dr Fink and Lisa Coleman.
That was definitely the Farfisa new wave sound that was happening at the time. We were pretty much using Oberheim OB-Xs to do that.