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

Vol. 2 3-181
INSTRUCTION SET REFERENCE, A-M
These two methods are discussed in the following sections. For methods that are avail-
able 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.
This method (introduced with Pentium 4 processors) returns an ASCII brand identifi-
cation string and the maximum operating frequency of the processor to the EAX,
EBX, ECX, and EDX registers.
Figure 3-8. Determination of Support for the Processor Brand String
OM15194
IF (EAX & 0x80000000)
CPUID
IF (EAX Return Value
≥ 0x80000004)
CPUID
Function
Supported
True ≥
Extended
EAX Return Value =
Max. Extended CPUID
Function Index
Input: EAX=
0x80000000
Processor Brand
String Not
Supported
False
Processor Brand
String Supported
True