FXSR

Architecture referenceFeex

FXSR dey identify di FXSAVE/FXRSTOR facility dem to save and restore old floating-point and SIMD state. Na operating-system state-management capability, no be application speed rating.

Wetin you need know

FXSR dey identify di FXSAVE/FXRSTOR facility dem to save and restore old floating-point and SIMD state. Na operating-system state-management capability, no be application speed rating.

How e dey work

FXSAVE dey write di defined x87, MMX, XMM and MXCSR state picture, and FXRSTOR dey restore di matching state. Di picture get standard layout and alignment. Di exact register set and format depend on execution mode and architecture control dem.

Where e dey useful

Operating system or runtime wey dey do low-level context handling must keep di state wey im execution environment allow. Normal application dem usually rely on OS and ABI instead of make dem save arbitrary context picture by diamselves.

How to check support and enablement

CPUID.01H:EDX bit 24 dey list FXSR. Low-level software must also follow di control-register, alignment and privilege rule dem inside di architecture manual. No replace OS context handling with application-level save/restore trick.

State-management facility dem na mainly OS and runtime responsibility. Buffer dem, mask dem, component size dem, alignment and restore rule dem must agree with di architecture and execution mode. To save only part fit spoil code wey dey use extra state wey dey enabled.

Wetin di feature no dey guarantee

FXSAVE picture no dey keep all later AVX, AVX-512 or AMX state. To treat am like complete modern context fit spoil program even wen FXSR dey supported. XSAVE-family state management na separate mechanism.

Compatibility and performance inside real life

Application-level feature detection suppose use runtime interface wey dem dey maintain wen e possible. Separate hardware support from OS enablement, and for dynamic feature dem, check process permission. CPU label alone no fit prove say any save/restore sequence correct.

Practical verification checklist

Record di exact processor or platform model plus di application, OS and runtime version dem wey dey involve. Make you keep di exact word dem wey di error or requirement use.
Check di manufacturer reference for dat exact model, den inspect di real capability and enabled state inside di environment where di program dey run.
Compare every single requirement of di binary or backend wey you choose. Name wey resemble am, alias, or broad technology label no reach.
Confirm say di application select di implementation wey dem intend. Use di diagnostics wey dem document and supported fallback if requirement dem no complete.
Make only one supported change at a time, den run di same workload again. Keep di original configuration and recovery way ready.

If dem list di feature but software no fit use am

Start from di exact component wey dey fail. Hardware database dey describe capability wey dem record; di operating system or hypervisor fit show different real environment. If illegal-instruction error happen, you still need to check di exact instruction wey cause di fault and di binary build, because corrupt file or anoda instruction wey no dey supported fit give di same kind problem.

Install di application, driver or runtime version wey get support for dat exact platform, and use di vendor documented baseline or fallback build if e need am. Software update no fit create instruction wey di processor no get. Firmware and security-policy change dem suppose follow di system manufacturer procedure and recovery plan, no be just any common optimization advice.

Sources and scope of dis explanation

Intel 64 and IA-32 Architectures Software Developer's Manual · x86-64 psABI: processor architecture and microarchitecture level dem

Dis reference dem establish architectural behavior and software requirement dem. Dem no dey independently verify every feature value for any linked hardware model page. For model support, use dat page manufacturer evidence and check di active system configuration. Dis article no supply benchmark, certification or independent review date.

Sources and verification

Editorial ownership: Feex. No independent review date dey recorded. How we dey do research.

Intel 64 and IA-32 Architectures Software Developer's Manual · Volume 1 and 2 describe di named instruction family dem and CPUID; Volume 3 describe state, paging, VMX and protection control dem. Architecture documentation no dey prove say particular model support am.
x86-64 psABI: processor architecture and microarchitecture level dem · Machine Interface, Processor Architecture: baseline and cumulative v2/v3/v4 feature table, OS-state check dem and deployment recommendation dem.

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