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Vol. 2A 3-181
INSTRUCTION SET REFERENCE, A-M
CPUID—CPU Identification
query maximum number of cores per physical package by executing CPUID with
EAX=4 and ECX=0.
INPUT EAX = 5: Returns MONITOR and MWAIT Features
When CPUID executes with EAX set to 5, the processor returns information about
features available to MONITOR/MWAIT instructions. The MONITOR instruction is used
for address-range monitoring in conjunction with MWAIT instruction. The MWAIT
instruction optionally provides additional extensions for advanced power manage-
ment. See Table 3-12.
INPUT EAX = 6: Returns Thermal and Power Management Features
When CPUID executes with EAX set to 6, the processor returns information about
thermal and power management features. See Table 3-12.
INPUT EAX = 10: Returns Architectural Performance Monitoring Features
When CPUID executes with EAX set to 10, the processor returns information about
support for architectural performance monitoring capabilities. Architectural perfor-
mance monitoring is supported if the version ID (see Table 3-12) is greater than
Pn 0. See Table 3-12.
For each version of architectural performance monitoring capability, software must
enumerate this leaf to discover the programming facilities and the architectural
performance events available in the processor. The details are described in Chapter
18, “Debugging and Performance Monitoring,” in the Intel® 64 and IA-32 Architec-
tures Software Developer’s Manual, Volume 3B.
METHODS FOR RETURNING BRANDING INFORMATION
Use the following techniques to access branding information:
1. Processor brand string method; this method also returns the processor’s
maximum operating frequency
2. Processor brand index; this method uses a software supplied brand string table.
These two methods are discussed in the following sections. For methods that are
available in early processors, see Section: “Identification of Earlier IA-32 Processors”
in Chapter 14 of the Intel® 64 and IA-32 Architectures Software Developer’s Manual,
Volume 1.
The Processor Brand String Method
Figure 3-8 describes the algorithm used for detection of the brand string. Processor
brand identification software should execute this algorithm on all Intel 64 and IA-32
processors.