The original "dead zone" was x'8000 0000' to x'FFFF FFFF'. I think I remember my first IARVx giving me address x'0000 0001 0000 0000', but that was long ago. This has been expanded up to the 32gb uh... border (x'0000 0008 0000 0000') some years ago. Rumor is Java uses this area to have 32gb of addressability using 32-bit (3-bit shifted) pointers.
But it was (and is) very wise to avoid using that range. In non-AMODE64 bit 32 is used as a flag, and as the AMODE bit for linking. sas On Fri, Nov 22, 2019 at 10:14 AM Dougie Lawson <[email protected]> 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.
