The “dead zone” is an OS-specific restriction. Processes running under
Linux on z/Architecture see the whole 64-bit address space, for example.
Keven
On Fri, Nov 22, 2019 at 4:23 PM -0600, "Paul Gilmartin"
<00000014e0e4a59b-dmarc-requ...@listserv.uga.edu> wrote:
On 2019-11-22, at 08:14:13, Dougie Lawson wrote:
>
> ABEND0C4 PIC38 is the fun one. You can't step into any 32-bit address as
> the 32nd bit was reserved by the MVS to MVS/XA change to mark whether we
> were in 24-bit or 31-bit.
>
> So the 64-bit guys decided that the easiest fix was to completely disallow
> any address from 8000000 through to 8FFFFFFF, which is an extremely good
> idea to avoid breaking 31-bit code.
>
Do I understand correctly that enforcement is entirely by
software; those addresses are quite acceptable to the hardware?
> They added PIC3A and PIC3B for the 64-bit page and segment exceptions (and
> we've seen a few of those with Db2).
-- gil
