CPUID—CPU Identification

INSTRUCTION SET REFERENCE, A-L

3-216 Vol. 2A

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-termi-
nated.

Figure 3-9.  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