>From PofOp: The set-address-space-control-fast facility consists of the SET ADDRESS SPACE CONTROL FAST (SACF) instruction, which possibly can be used instead of the previously existing SET ADDRESS SPACE CONTROL (SAC) instruction, depending on whether all of the SAC functions are required. SACF, unlike SAC, does not perform the serialization and checkpoint-synchronization functions, nor does it cause copies of prefetched instructions to be discarded. SACF provides improved performance on some models.
OK, so ... "on some models". Is this one of those "It used to matter, but doesn't any more" deals, or should we still think about using SACF when appropriate? I did find this in an old post to ASM370-L: As I understand it SACF was only implemented (as different from SAC) on a few models. The basic difference in how the instruction prefetch queue is handled. If you are not modifying the instruction stream or switching from home to primary (which causes instruction fetch to load from a different memory) there should not be a difference. And do the serialization caveats mean that in cases where we have absolutely no expectation of data change in the target address space (as in, "If they do that after calling us, all bets are off anyway"), SACF would be appropriate? Thanks for any insights! -- ...phsiii ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
