Bad idea. The 31bit bar is there for a very, very good reason.

Tony Thigpen

Paul Edwards wrote on 05/06/2018 02:51 PM:
Hi. I would like to submit an RFE to IBM to
support a LOC=32 parameter to GETMAIN,
giving 32-bit programs access to a full 4 GiB
instead of the current 2 GiB provided by
LOC=31. IBM can use the LOC=31 bits
plus the top bit of the option byte seen here:

https://www.ibm.com/support/knowledgecenter/SSLTBW_2.3.0/com.ibm.zos.v2r3.ieav200/svc120.htm

When the GETMAIN is executed in AM64,
memory above 2 GiB is potentially returned.
When executed in AM31, normal LOC=31
memory is obtained instead. This way the
application will still work on older systems
that aren't LOC=32 aware.

When obtaining LOC=32 memory, the GETMAIN
routine should search *down* the free memory
chain to find a free area, to preserve the LOC=31
space.

It is up to the application program to ensure that
when manipulating the LOC=32 memory it is in
AM64 and while in AM64 it does not attempt to
use the top bit of any 32-bit register as a flag.

After I submit the RFE it would be good if people
could upvote it. What is the best wording I can
use so that IBM understands what I am asking
for and doesn't reject it?

Thanks. Paul.

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