Intel 64 and IA-32 Architectures Software Developers Manual Volume 2A, Instruction Set Reference, A-M

Vol. 2 3-639
INSTRUCTION SET REFERENCE, A-M
MOVNTI—Store Doubleword Using Non-Temporal Hint
Description
Moves the doubleword integer in the source operand (second operand) to the desti-
nation operand (first operand) using a non-temporal hint to minimize cache pollution
during the write to memory. The source operand is a general-purpose register. The
destination operand is a 32-bit memory location.
The non-temporal hint is implemented by using a write combining (WC) memory
type protocol when writing the data to memory. Using this protocol, the processor
does not write the data into the cache hierarchy, nor does it fetch the corresponding
cache line from memory into the cache hierarchy. The memory type of the region
being written to can override the non-temporal hint, if the memory address specified
for the non-temporal store is in an uncacheable (UC) or write protected (WP)
memory region. For more information on non-temporal stores, see “Caching of
Temporal vs. Non-Temporal Data” in Chapter 10 in the Intel® 64 and IA-32 Architec-
tures Software Developer’s Manual, Volume 1.
Because the WC protocol uses a weakly-ordered memory consistency model, a
fencing operation implemented with the SFENCE or MFENCE instruction should be
used in conjunction with MOVNTI instructions if multiple processors might use
different memory types to read/write the destination memory locations.
In 64-bit mode, the instruction’s default operation size is 32 bits. Use of the REX.R
prefix permits access to additional registers (R8-R15). Use of the REX.W prefix
promotes operation to 64 bits. See the summary chart at the beginning of this
section for encoding data and limits.
Operation
DEST ← SRC;
Intel C/C++ Compiler Intrinsic Equivalent
MOVNTDQ void_mm_stream_si32 (int *p, int a)
Opcode Instruction
64-Bit
Mode
Compat/
Leg Mode Description
0F C3 /r MOVNTI m32,
r32
Valid Valid Move doubleword from r32
to m32 using non-temporal
hint.
REX.W + 0F C3 /r MOVNTI m64,
r64
Valid N.E. Move quadword from r64 to
m64 using non-temporal hint.