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System

WRMSRNS

A model-specific register write that, unlike WRMSR, is not serializing.

CPUID
WRMSRNS
CPUID.(EAX=07H,ECX=1):EAX[19]
Instructions
1 mnemonic
Processors
Panther Lake, Nova Lake, Diamond Rapids, Sierra Forest, Clearwater Forest

WRMSR is a serializing instruction: it waits until all earlier instructions are done and all buffered writes are drained. Most MSR writes do not need that. WRMSRNS writes an MSR the same way but without serializing, while still guaranteeing that instructions before it see the old value and instructions after it the new one. Code that used WRMSR as a serializing point can use SERIALIZE instead. The immediate form of WRMSRNS belongs to MSR_IMM.

Instructions

Mnemonics with at least one form in WRMSRNS. Each page lists all forms of the mnemonic, including those of other extensions.
MnemonicSummaryForms
WRMSRNSWrites a model-specific register like WRMSR but without serializing the processor; the MSR_IMM form takes the MSR number as an immediate.1

CPUID and processors

XED splits WRMSRNS into 1 ISA set. Software can use a form when the processor reports every CPUID bit of one alternative of the form's ISA set.

XED ISA sets of WRMSRNS. Alternatives are separated by “or”; processors follow XED’s chip model, which covers AMD processors up to Zen 2.
ISA setCPUIDProcessors in XED
WRMSRNS

WRMSRNS
CPUID.(EAX=07H,ECX=1):EAX[19] WRMSRNS

Panther Lake, Nova Lake, Diamond Rapids, Sierra Forest, Clearwater Forest

Sources

  1. Intel XED v2026.08.23 (commit 0bcb6237345c): forms, encodings, ISA sets, CPUID bits and chip model.
  2. Intel 64 and IA-32 Architectures Software Developer's Manual, Volume 2 (325383-092, June 2026)

The tables are derived from Intel XED, Copyright Intel Corporation, licensed under the Apache License 2.0; x86-64.net converted and reformatted them. The text is our own.