EDX From CPUID Leaf 1

Executing the cpuid instruction with 1 in eax produces feature flags in edx. These are the original processor features that cpuid can report. Many are so long established that modern versions of Windows will not start without them.

Indeed, 64-bit Windows started with the luxury of requiring most of them up-front. If any of the feature bits marked below with “required” in parentheses is not set when the 64-bit kernel initialises its support for a processor, Windows stops with the bug check UNSUPPORTED_PROCESSOR (0x5D). For 32-bit Windows, requirement of features is not nearly so immediate. Each processor is first evaluated, and not just from this leaf, to build a list of the kernel’s own notion of feature bits such as would be saved as the FeatureBits member of the processor’s KPRCB. The 32-bit kernel’s eventual rejection of a processor is decided from these feature bits, not directly from the cpuid feature flags. Details may eventually follow the table as notes on each feature flag.

Mask	Intel’s Symbolic Name	Versions (x86)	Versions (x64)
0x00000001	FPU		all (required)
0x00000002	VME	3.50 and higher
0x00000004	DE		all (required)
0x00000008	PSE	4.0 and higher	all (required)
0x00000010	TSC	3.50 and higher	all (required)
0x00000020	MSR		all (required)
0x00000040	PAE		all (required)
0x00000080	MCE	3.50 to 3.51	all (required)
0x00000100	CX8	4.0 and higher	all (required)
0x00000200	APIC		all (required)
0x00000800	SEP	5.1 and higher
0x00001000	MTRR	4.0 and higher	all (required)
0x00002000	PGE	4.0 and higher	all (required)
0x00004000	MCA		all (required)
0x00008000	CMOV	4.0 and higher	all (required)
0x00010000	PAT	5.0 and higher	all (required)
0x00080000	CLFSH	6.0 and higher	all (required)
0x00200000	DS	5.1 and higher	all
0x00800000	MMX	4.0 and higher	all (required)
0x01000000	FXSR	5.0 and higher	all (required)
0x02000000	SSE	5.0 and higher	all (required)
0x04000000	SSE2	5.1 and higher	all (required)
0x10000000	HTT	5.1 and higher	all

To be clear, version 3.10 does not test for any cpuid feature flag. Its only interest in cpuid leaf 1 is to get the family, model and stepping from eax. For 64-bit Windows, “all” starts with the version 5.2 from Windows Server 2003 SP1.

PSE-36 (Bit 17)

AMD’s documentation omits the hyphen. No Windows kernel is known to use this feature.

PSN (Bit 18)

AMD’s documentation has this bit as reserved. No Windows kernel is known to use this feature.

ACPI (Bit 22)

AMD’s documentation has this bit as reserved. No Windows kernel is known to use this feature.

SS (Bit 27)

AMD’s documentation has this bit as reserved. No Windows kernel is known to use this feature.