> > Apple II+ PROM Blaster Software > > 24-Pin Unit: Rev 4.1 > > 28-Pin Unit: Rev 1.2 As it turns out, I happen to have both of these cards. The 24 pin unit has Personality Modules to select the type of eprom being read/programmed, and, the 28 pin uses 3 jumpers to select type of eprom. Bill Garber from GS-Electronics http://www.garberstreet.com