This content has not been validated; it was AI-generated following the x86-64 ISA Documentation generation process to maintain high quality. However, as no human has verified this data, errors may exist. If the accuracy of this data is critical, please consult the Intel SDM. The model used to generate this is gemma4:31b

INSW

Stores the word from the source operand into the destination word-sized memory location and increments or decrements the index register (SI/DI) based on the direction flag (DF).

The following table covers what the source and destinations can be:

DO NOT support LOCK

This instruction is available in 16-bit operand size mode. In x86-64, it is only supported when the processor is operating in compatibility mode or when the current privilege level is operating with a 16-bit operand size override.

The index registers used for the memory operands are restricted to ESI/EDI (or SI/DI in 16-bit mode). The behavior of the pointer increment/decrement is strictly tied to the state of the DF bit in the RFLAGS register. Failure to correctly initialize the direction flag may result in unintended memory corruption.