Intel 64 and IA-32 Architectures Software Developers Manual Volume 2A, Instruction Set Reference, A-M

Vol. 2 3-167
INSTRUCTION SET REFERENCE, A-M
INPUT EAX = 0: Returns CPUID’s Highest Value for Basic Processor Information and
the Vendor Identification String
When CPUID executes with EAX set to 0, the processor returns the highest value the
CPUID recognizes for returning basic processor information. The value is returned in
the EAX register (see Table 3-13) and is processor specific.
80000006H EAX
EBX
ECX
EDX
Reserved = 0
Reserved = 0
Bits 7-0: Cache Line size in bytes
Bits 15-12: L2 Associativity field *
Bits 31-16: Cache size in 1K units
Reserved = 0
NOTES:
*L2 associativity field encodings:
00H - Disabled
01H - Direct mapped
02H - 2-way
04H - 4-way
06H - 8-way
08H - 16-way
0FH - Fully associative
80000007H EAX
EBX
ECX
EDX
Reserved = 0
Reserved = 0
Reserved = 0
Reserved = 0
80000008H EAX
EBX
ECX
EDX
Virtual/Physical Address size
Bits 7-0: #Physical Address Bits*
Bits 15-8: #Virtual Address Bits
Bits 31-16: Reserved = 0
Reserved = 0
Reserved = 0
Reserved = 0
NOTES:
* If CPUID.80000008H:EAX[7:0] is supported, the maximum physical
address number supported should come from this field.
Table 3-12. Information Returned by CPUID Instruction (Contd.)
Initial EAX
Value Information Provided about the Processor