Well, a S/360 program that depends on getting PIC 06 for an unaligned load won't work correctly on a 360/85 or S/370. S/370 supported 2 KiB pages, and those are history. MVS/370 uses SIO, whch only exists in S/370 mode: also history. So carrying an old OS forward has always has issues. Sure, IBM could ensure absolute compatibiity for old releaes, but TANSTAAFL. Only IBM knows what the extra cost would be, but I guaranty that there would be an extra cost.
I'm sure that this has been discussed at Share. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> on behalf of Tony Thigpen <t...@vse2pdf.com> Sent: Tuesday, September 1, 2020 5:20 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: Architectural Level Sets I was thinking more along the lines of things that prevented earlier operating systems from even IPLing on newer boxes. Such as z13 is the last processor to have ESA/390 mode. I also have it in my head that at some point there were changes to the page size and virtual storage tables that caused havoc. Tony Thigpen Seymour J Metz wrote on 9/1/20 3:30 PM: > Typically the new features reqiured by a level set were added over several > generations, and each generation added more than one feature. > > > -- > Shmuel (Seymour J.) Metz > http://mason.gmu.edu/~smetz3 > > > ________________________________________ > From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> on behalf of > Tony Thigpen <t...@vse2pdf.com> > Sent: Tuesday, September 1, 2020 3:25 PM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Architectural Level Sets > > IBM has had several Architectural Level Set points where there were > significant changes to the CPU that prevented earlier operating systems > from running on them. > > What CPU's were involved with each level, and what was the real > underlying item changed on the CPU that forced a new level? (Let's keep > it limited to z990 and newer.) > > > Tony Thigpen > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
