Intel 253666-024US - Manual (Page 706)

3-660 Vol. 2A MOVNTQ—Store of Quadword Using Non-Temporal Hint
INSTRUCTION SET REFERENCE, A-M
MOVNTQ—Store of Quadword Using Non-Temporal Hint
Description
Moves the quadword in the source operand (second operand) to the destination
operand (first operand) using a non-temporal hint to minimize cache pollution during
the write to memory. The source operand is an MMX technology register, which is
assumed to contain packed integer data (packed bytes, words, or doublewords). The
destination operand is a 64-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 MOVNTQ instructions if multiple processors might use
different memory types to read/write the destination memory locations.
This instruction’s operation is the same in non-64-bit modes and 64-bit mode.
Operation
DEST ← SRC;
Intel C/C++ Compiler Intrinsic Equivalent
MOVNTQ void _mm_stream_pi(__m64 * p, __m64 a)
SIMD Floating-Point Exceptions
None.
Protected Mode Exceptions
#GP(0) For an illegal memory operand effective address in the CS, DS,
ES, FS or GS segments.
Opcode Instruction 64-Bit
Mode
Compat/
Leg Mode
Description
0F E7 /r MOVNTQ m64,
mm
Valid Valid Move quadword from mm to m64 using
non-temporal hint.