Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1067

mf
mf — Memory Fence
( ) mf
Format: qp
( ) mf.a
qp
This instruction forces ordering between prior and subsequent memory accesses. The
Description:
ordering_form ensures all prior data memory accesses are made visible prior to any
subsequent data memory accesses being made visible. It does not ensure prior data
memory references have been accepted by the external platform, nor that prior data
memory references are visible.
The acceptance_form prevents any subsequent data memory accesses by the processor
from initiating transactions to the external platform until:
• all prior loads to sequential pages have returned data, and
• all prior stores to sequential pages have been accepted by the external platform.
The definition of "acceptance" is platform dependent. The acceptance_form is typically
used to ensure the processor has "waited" until a memory-mapped I/O transaction has
been "accepted" before initiating additional external transactions. The acceptance_form
does not ensure ordering, or acceptance to memory areas other than sequential pages.
Operation: if (PR[qp]){
if (acceptance_form)
acceptance_fence();
else // ordering_form
ordering_fence();
}
None
Interruptions:
3:168
ordering_form M24
acceptance_form M24
Volume 3: Instruction Reference