Extensions
Forms
1 (1 VEX)
Data
Intel XED v2026.08.23

Forms

Every encoding of VSTMXCSR that Intel XED knows, one row per XED instruction form (iform). How to read the notation.
InstructionEncodingRequires
VSTMXCSR m32 VSTMXCSR_MEMdVEX.LZ.NP.0F.WIG AE /3AVX

Operation

What the forms do, in pseudocode that our tests run against results recorded on real processors. How to read.

dest.write(mxcsr)                    # the bits it lacks as zeros

Run on AMD Zen 5 (EPYC 9645): 2 cases.

Operands

What each form reads and writes, as Intel XED records it: the operands of its syntax, in order, and the implicit ones that the syntax does not name. How to read.
OperandKindAction
VSTMXCSR m32
m32explicitwrite
MXCSRimplicitread

Flags

None: XED records no flag that the forms test or change.

Exceptions

The exception class is XED's name for the set of exception conditions that a form follows. How to read.

All forms
avx-type-5

CPUID and processors

Each form belongs to an XED ISA set. A form can be used when the processor reports every CPUID bit of one of its ISA set's alternatives.

CPUID requirements and processors of the XED ISA sets above. Alternatives are separated by “or”; processors follow XED’s chip model, whose AMD processors end with Zen 2, and the CPU data of this site for Zen 3 to Zen 6.

More AVX instructions

All 253 AVX instructions

Sources

  1. Intel XED v2026.08.23 (commit 0bcb6237345c): forms, encodings, operands, flags, exception classes, attributes, ISA sets, CPUID bits and chip model.
  2. The CPU data of x86-64.net: Zen 3 to Zen 6, from GCC’s -march feature sets and AMD’s Processor Programming References, which the page of each processor cites.
  3. Intel 64 and IA-32 Architectures Software Developer's Manual, Volume 2 (325383-093, September 2026): Volume 2B, page 4-676 (STMXCSR)
  4. Intel 64 and IA-32 Architectures Software Developer's Manual, Volume 1 (253665-093, September 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.