<>It goes into Q-Bus based PDP11 systems. I know it will work with <>an 11/73 and 11/83. It may work in other systems as well. Totally incompatable with J11 cpu. <The FPF11 board has a ribbon cable which ends in a connector which <fits the Floating point chip socket of a 11/23, 11/23+ and 11/24. < < Megan Gentry < Former RT-11 Developer Confirmed in the LSI-11 systems service manuals. Allison