Computer Hardware User's Manual

3-182 Vol. 2A CPUID—CPU Identification
INSTRUCTION SET REFERENCE, A-M
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.
How Brand Strings Work
To use the brand string method, execute CPUID with EAX input of 8000002H through
80000004H. For each input value, CPUID returns 16 ASCII characters using EAX,
EBX, ECX, and EDX. The returned string will be NULL-terminated.
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