I can clarify that somewhat ... From its inception in 1988, OS/400 (the operating system of the AS/400, AS/400e, iSeries, System i ...) has had a "System/36 Environment", including an OCL interpreter, and an RPG II compile, so you could "port"most of your System/36 applications over to OS/400 and run them there. But, you had to move "source code" and recompile. So, this is not an "emulator" or "simulator" but a "runtime environment". That option was not too popular with IBM's S/36 customers, in the early years, because of the higher cost of the AS/400 systems, and the effort involved. Also, this did not allow migrating any "assembler" subroutines. Also, the performance was not fabulous on the IMPI CISC-based AS/400 machines. So, starting with V3R7 and the first RISC-based AS/400s, IBM introduced the "Advanced 36" models -- this provided a true emulator or "virtual machine" -- you could install this Advanced 36 emulator directly on top of the hardware (the SLIC kernel) on the model 236, or on the 436, you could run OS/400 and up to three S/36 "virtual machines" (under OS/400). Support for these *M36 virtual machines continued from V3R7 through V4R4, or a span of about10 years. IBM felt this was sufficient time to allow most S/36 customers to migrate their applications and convert them to "native" OS/400 applications. Amazingly, there are still quite a few satisfied customers running their S/36 applications on these *M36 virtual machines under OS/400. This is a very faithful reproduction (emulation) of the original System/36 hardware, since it was developed by IBM Rochester Laboratory, where the original S/3, S/32, S/34 and S/36 were developed -- so the developers had access to all of the hardware designs, microcode listings, and software source code, etc. -- AFAIK, customers could migrate and run 100% of their S/36 applications to the Advanced 36 *M36 virtual machine running under SSP 7.1 or 7.5. (IBM has a long and rich history of writing emulators and simulators -- when the IBM System/360 family was introduced, various models of 360 supported emulators for the 1401,, 7094, etc. 0 IBM's previous generation of "mainframes").