Thanks. I don't have access to a modern system to try it out, but I
first thought that the use of the high bits depended on the instruction
used, such as STMG versus STM.
I suppose I'm trying to understand enough to write code that's easy to
update.
Roops
On 24/11/2020 15:09, Gary Weinhold wrote:
A short answer is so the hardware knows to use the 64-bit address in
the 64-bit register instead of just the last 31-bits (AMODE-31).
On 2020-11-24 9:38 a.m., Rupert Reynolds wrote:
Reading (a lot of) documentation from IBM it seems that a lot has
gone into the *nix side of z/OS and extra instructions and 64-bit
addrssability for data, but that the code itself still resides below
the bar, so that most AMODE 24 and 31 code from years ago will still
compile/assemble and run as is, or with minimal change.
Is that fair?
But if new code using 64-bit data is still loaded and executed below
the bar, and new instructions and extended registers handle the
addressing of data with 64-bit addresses, why is there an AMODE 64 at
all? Is it simply to indicate that a larger (DS 18D) savearea should
be provided, as it may be needed by the called program?
Thanks for any clarification you can offer.
Roops
Gary Weinhold
Senior Application Architect
DATAKINETICS | Data Performance & Optimization
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