11-6
PROCESSOR IDENTIFICATION AND FEATURE DETERMINATION
3 in the Model ID field. Future P6-family processors are indicated by a 6 in the Family ID
and a value greater than 3 in the Model ID field.
Figure 11-2 shows the feature information bit fields returned by CPUID in EAX.
Table 11-2 describes the bit representations for the new P6-family processor features.
31
1211
0807
0403
00
Reserved (0)
Family ID
Model ID
Stepping ID
Figure 11-1. EAX Return Values
32625242322
-
19
18171615141312111009080706050403020100
Reserved
(0)
Figure 11-2. CPUID Feature Field Information Bits
Table 11-2. New P6-Family Processor Feature Information Returned by CPUID in EDX
BitFeatureValueDescription
Notes
11SEP1Fast System CallIndicates whether the processor supports the Fast
System Call instructions SYSENTER and SYSEXIT.
16PAT1Page Attribute
Table
Indicates whether the processor supports the Page
Attribute Table. This feature augments the Memory
Type Range Registers (MTRRs), allowing an
operating system to specify attributes of memory on a
page granularity through a linear address.
17PSE-36136-bit Page Size
Extension
Indicates whether the processor supports 4 MB pages
that are capable of addressing physical memory
beyond 4 GB. This feature indicates that the up-per
four bits of the physical address of the 4-MB page is
encoded by bits 13-16 of the page directory entry.
18PN
1Processor
Number
Indicates whether the processor supports the 96-bit
Processor Number feature.
19-22
rsvd
0
Reserved
These bits are reserved for future use. The contents of
these fields are not defined and should not be relied
upon or altered.
23MMX1MMX-technologyIndicates whether the processor supports the MMX
?
technology instruction set and architecture.
24FXSR1Fast floating-
point save and
restore
Indicates whether the processor supports the
FXSAVE and FXRSTOR instructions for fast save and
restore of the floating-point context. Presence of this
bit also indicates that CR4.OSFXSR is available,
allowing an operating system to indicate that it uses
the fast save/restore instructions.
25XMM1Streaming SIMD
Extension
Indicates whether the processor supports the
Streaming SIMD Extensions instruction set.
