My interpretation from the BTSJ port was that it was a cheater port more analogous to Cygwin that ran on top of MVS rather than a "real" VM guest but it's been several years since I read the paper. I have some private correspondence from Dick Johnson who worked on a port of OSF/1 that was marketed as AIX/ESA: "I'll give you a little AIX/ESA history and try to answer your questions. I currently volunteer at the Computer History Museum, so I am a bit of a computer history buff myself. Starting in the late 1980s I was working at IBM SSD in San Jose. The IBM Palo Alto Scientific Center had developed AIX/370 (my neighbor Wally Iimura was one of the developers) to compete with Amdahl UTS, and the decision was made to create a major UNIX offering for the IBM mainframe based on the OSF/1 kernel from CMU. I was the leader of a group in San Jose that did the AIX/ESA device support for all the storage devices (DASD and tape). The bulk of AIX/ESA development was carried out by a large group of several hundred in Kingston, NY. The AIX/ESA code base was almost completely different from that of AIX/370 and AIX for the RS/6000 (there had been an effort to port the RS/6000 AIX to the mainframe that was abandoned). When it was released, the product did not sell well, and never exceeded 35 customer licenses. This was for many reasons. Marketing did not push it, and the MVS people created Open MVS that allowed UNIX to run in MVS. However the AIX/ESA OS itself was very solid and we routinely handed a workload of over 1000 logged on users on a single IBM mainframe. All the usual UNIX environment was provided. My group did the device drivers that supported DASD up to the 3390 and also the tape drives and tape library then selling. AIX/370 multi-processor support was fairly primitive (there was only a single kernel lock), but AIX/ESA had complete multi-processor and multi-threading support. There was a complete of manuals that went with the AIX/ESA product. There was the usual Operators Guide, User's Guide, etc. They had Navy blue covers, but I did not keep any of them myself. I do not know of any place to find soft copy of any of them. I believe the product was shipped only on tape. As a developer I installed AIX/ESA many times, but I was always using VM for this. The combination of being able to run it in a virtual machine along with the PER hardware of the mainframe made it pretty easy to debug problems. Even though the product was not a success, I was proud of our work on it and really enjoyed the work." Regards, On Wed, Nov 22, 2017 at 8:38 AM, Noel Chiappa <jnc(a)mercury.lcs.mit.edu> wrote: