x86 Instruction Set Reference

# MOVNTDQ

# Store Double Quadword Using Non-Temporal Hint

Opcode Mnemonic Description
66 0F E7 /r MOVNTDQ m128, xmm Move double quadword from xmm to m128 using nontemporal hint.

# Description

Moves the double quadword in the source operand (second operand) to the destination operand (first operand) using a non-temporal hint to prevent caching of the data during the write to memory. The source operand is an XMM register, which is assumed to contain integer data (packed bytes, words, doublewords, or quadwords). The destination operand is a 128-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 IA-32 Intel Architecture 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 MOVNTDQ instructions if multiple processors might use different memory types to read/write the destination memory locations.

# Operation

Destination = Source;
1
2

# 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. If a memory operand is not aligned on a 16-byte boundary, regardless of segment.
#GP(0) For an illegal memory operand effective address in the CS, DS, ES, FS or GS segments. If a memory operand is not aligned on a 16-byte boundary, regardless of segment.
#SS(0) For an illegal address in the SS segment.
#PF(fault-code) For a page fault.
#NM If TS in CR0 is set.

# Real-Address Mode Exceptions
#GP(0) If a memory operand is not aligned on a 16-byte boundary, regardless of segment. If any part of the operand lies outside the effective address space from 0 to FFFFH.
#GP(0) If a memory operand is not aligned on a 16-byte boundary, regardless of segment. If any part of the operand lies outside the effective address space from 0 to FFFFH.
#NM If TS in CR0 is set.

# Virtual-8086 Mode Exceptions

Same exceptions as in Real Address Mode
#PF(fault-code) For a page fault.

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