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

3-162 Vol. 2
INSTRUCTION SET REFERENCE, A-M
03H EAX
EBX
ECX
EDX
Reserved.
Reserved.
Bits 00-31 of 96 bit processor serial number. (Available in Pentium III
processor only; otherwise, the value in this register is reserved.)
Bits 32-63 of 96 bit processor serial number. (Available in Pentium III
processor only; otherwise, the value in this register is reserved.)
NOTE:
Processor serial number (PSN) is not supported in the Pentium 4
processor or later. On all models, use the PSN flag (returned using
CPUID) to check for PSN support before accessing the feature. See AP-
485, Intel Processor Identification and the CPUID Instruction (Order
Number 241618) for more information on PSN.
Table 3-12. Information Returned by CPUID Instruction (Contd.)
Initial EAX
Value Information Provided about the Processor