I think this happened with the move to MVS/XA as XA does not recognise a BC mode PSW. So I guess it was the first machine which did not support architectures earlier than MVS/XA. I suspect that was the 3081.
All my conjecture of course. Let's see what the IBM oracles tell us. Lennie Dymoke-Bradshaw -----Original Message----- From: IBM Mainframe Discussion List <[email protected]> On Behalf Of Mark S Waterbury Sent: 09 September 2020 18:35 To: [email protected] Subject: Re: Architectural Level Sets To add to this thread ... I would like to know at what point during the evolution from S/370 to S/370-XA to S/390 to zSeries, did the architecture stop supporting IPL of any OS that runs in "BC mode" or that starts out in BC mode, before setting up page and segment tables and control registers and then enabling DAT? In other words, what processor family(s) and specific models in that family, if need be, can no longer IPL and run any of the "public domain" operating systems from the 1970s to early 1980s? (DOS/360, OS/360, DOS/VS, OS/VS1, OS/VS2, VM/370, TSS/370, etc.) Thanks in advance. Mark S. Waterbury ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
