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Module core.cpuid

Identify the characteristics of the host CPU, providing information about cache sizes and assembly optimisation hints. This module is provided primarily for assembly language programmers.


Some of this information was extremely difficult to track down. Some of the documents below were found only in cached versions stored by search engines! This code relies on information found in:

  • "Intel(R) 64 and IA-32 Architectures Software Developers Manual, Volume 2A: Instruction Set Reference, A-M" (2007).
  • "AMD CPUID Specification", Advanced Micro Devices, Rev 2.28 (2008).
  • "AMD Processor Recognition Application Note For Processors Prior to AMD Family 0Fh Processors", Advanced Micro Devices, Rev 3.13 (2005).
  • "AMD Geode(TM) GX Processors Data Book", Advanced Micro Devices, Publication ID 31505E, (2005).
  • "AMD K6 Processor Code Optimisation", Advanced Micro Devices, Rev D (2000).
  • "Application note 106: Software Customization for the 6x86 Family", Cyrix Corporation, Rev 1.5 (1998)
  • "Geode(TM) GX1 Processor Series Low Power Integrated X86 Solution", National Semiconductor, (2002)
  • "The VIA Isaiah Architecture", G. Glenn Henry, Centaur Technology, Inc (2008).
  • "What every programmer should know about memory", Ulrich Depper, Red Hat, Inc., (2007).
  • "CPU Identification by the Windows Kernel", G. Chappell (2009).
  • "Intel(R) Processor Identification and the CPUID Instruction, Application Note 485" (2009).


Currently only works on x86 and Itanium CPUs. Many processors have bugs in their microcode for the CPUID instruction, so sometimes the cache information may be incorrect.


aes() Is AES supported
amd3dnow() Is AMD 3DNOW supported?
amd3dnowExt() Is AMD 3DNOW Ext supported?
amdMmx() Are AMD extensions to MMX supported?
avx() Is AVX supported
avx2() Is AVX2 supported
avx512f() Is AVX512F supported
cacheLevels() The number of cache levels in the CPU.
coresPerCPU() Returns number of cores in CPU
dataCaches() The data caches. If there are fewer than 5 physical caches levels, the remaining levels are set to size_t.max (== entire memory space)
fma() Is FMA supported
fp16c() Is FP16C supported
has3dnowPrefetch() Is 3DNow prefetch supported?
hasCmov() Is cmov supported?
hasCmpxchg16b() Is cmpxchg8b supported?
hasCmpxchg8b() Is cmpxchg8b supported?
hasFxsr() Is fxsave/fxrstor supported?
hasLahfSahf() Are LAHF and SAHF supported in 64-bit mode?
hasLzcnt() Is LZCNT supported?
hasPclmulqdq() Is pclmulqdq supported
hasPopcnt() Is POPCNT supported?
hasRdrand() Is rdrand supported
hasRdseed() Is rdseed supported
hasRdtsc() Is rdtsc supported?
hasSha() Is SHA supported
hasSysEnterSysExit() Is SYSENTER/SYSEXIT supported?
hasVpclmulqdq() Is vpclmulqdq supported
hle() Is HLE (hardware lock elision) supported
hyperThreading() Is hyperthreading supported?
isItanium() Is this an IA64 (Itanium) processor?
isX86_64() Is this an Intel64 or AMD 64?
mmx() Is MMX supported?
preferAthlon() Optimisation hints for assembly code.
preferPentium1() Does this CPU perform better on Pentium I code than Pentium Pro code?
preferPentium4() Does this CPU perform better on Pentium4 code than PentiumPro..Core2 code?
processor() Returns processor string, for display purposes only
rtm() Is RTM (restricted transactional memory) supported
sse() Is SSE supported?
sse2() Is SSE2 supported?
sse3() Is SSE3 supported?
sse41() Is SSE4.1 supported?
sse42() Is SSE4.2 supported?
sse4a() Is SSE4a supported?
ssse3() Is SSSE3 supported?
threadsPerCPU() Returns number of threads per CPU
vaes() Is VEX-Encoded AES supported
vendor() Returns vendor string, for display purposes only. Do NOT use this to determine features! Note that some CPUs have programmable vendorIDs.
x87onChip() Does it have an x87 FPU on-chip?


CacheInfo Cache size and behaviour

Global variables

datacache CacheInfo[5] Scheduled for deprecation. Please use dataCaches instead.
family uint Warning: This field will be turned into a property in a future release.
model uint Warning: This field will be turned into a property in a future release.
numCacheLevels uint This field has been deprecated. Please use cacheLevels instead.
stepping uint Warning: This field will be turned into a property in a future release.


Don Clugston, Tomas Lindquist Olsen <>


Boost License 1.0