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

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INSTRUCTION SET REFERENCE, A-M
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.
Table 3-18 shows the brand string that is returned by the first processor in the
Pentium 4 processor family.
Extracting the Maximum Processor Frequency from Brand Strings
Figure 3-9 provides an algorithm which software can use to extract the maximum
processor operating frequency from the processor brand string.
NOTE
When a frequency is given in a brand string, it is the maximum
qualified frequency of the processor, not the frequency at which the
processor is currently running.
Table 3-18. Processor Brand String Returned with Pentium 4 Processor
EAX Input Value Return Values ASCII Equivalent
80000002H EAX = 20202020H
EBX = 20202020H
ECX = 20202020H
EDX = 6E492020H
“”
“ ”
“ ”
“nI ”
80000003H EAX = 286C6574H
EBX = 50202952H
ECX = 69746E65H
EDX = 52286D75H
“(let”
“P )R”
“itne”
“R(mu”
80000004H EAX = 20342029H
EBX = 20555043H
ECX = 30303531H
EDX = 007A484DH
“ 4 )”
“ UPC”
“0051”
“\0zHM”