On Tue, 22 Oct 2024 12:30:42 -0400 Tony Harminc <[email protected]> wrote:
:>On Tue, 22 Oct 2024 at 07:30, Seymour J Metz <[email protected]> wrote: :>> R1 designates an even/odd pair. However, the 256-byte alignment :>> requirement makes this less attractive. :>Ah yes, I had forgotten about that. And I shouldn't have, because I got :>burned by it when using TROT a few years ago. I have no idea why IBM :>would've designed it to silently ignore an incorrect boundary rather than :>giving a specification exception. "The rightmost bits of the register that are not used to form the address, which are bits 61-63 in the doubleword case and bits 52-63 in the 4 K-byte case, are ignored but should contain zeros; otherwise, the program may not operate compatibly in the future." Seems like sometimes IBM ignores the unused bits and in other cases generates an exception - such as MVST which documents "The ending character to be used to determine the end of the second operand is specified in bit positions 56-63 of general register 0. Bit positions 32-55 of general register 0 are reserved for possible future extensions and must contain all zeros; otherwise, a specification exception is recognized." -- Binyamin Dissen <[email protected]> http://www.dissensoftware.com Director, Dissen Software, Bar & Grill - Israel ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
