370 supported DAS (the code is in MVS3.8J).

43XX running MVS supported DAS also. 4381 could have up to 64M of main
storage...

Joe

On Tue, Sep 1, 2020 at 4:26 PM Mike Schwab <mike.a.sch...@gmail.com> wrote:

> Well, XA+ machines only supported 4K pages / 1M segments and not 2K
> pages / 64K segments.  Then DAS and Access register additions.  The
> 43xx series only supported a single virtual address space, like
> DOS/VSE.  3090s were the only processors to support Vector
> instructions, and op codes were re-used in z series.
>
> On Tue, Sep 1, 2020 at 4:20 PM Tony Thigpen <t...@vse2pdf.com> wrote:
> >
> > 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
> > >
> > > ----------------------------------------------------------------------
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> >
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>
>
> --
> Mike A Schwab, Springfield IL USA
> Where do Forest Rangers go to get away from it all?
>
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