Intel IA-32 Manuale Utente

9-42 Vol. 3A

In addition to verifying the processor signature, the intended processor platform type must be
determined to properly target the microcode update. The intended processor platform type is
determined by reading the IA32_PLATFORM_ID register, (MSR 17H).  This 64-bit register
must be read using the RDMSR instruction. 

The three platform ID bits, when read as a binary coded decimal (BCD) number, indicate the bit
position in the microcode update header’s processor flags field associated with the installed
processor.  The processor flags in the 48-byte header and the processor flags field associated
with the extended processor signature structures may have multiple bits set. Each set bit repre-
sents a different platform ID that the update supports.

MSR Address:

017H

Access:

Read Only

IA32_PLATFORM_ID is a 64-bit register accessed only when referenced as a Qword through a
RDMSR instruction.

To validate the platform information, software may implement an algorithm similar to the algo-
rithms in Example 9-6.

63:53

Reserved

52:50

Platform Id Bits (RO). The field gives information concerning the intended platform for the 
processor. See also Table 9-7.

5251 50
000Processor Flag 0
001Processor Flag 1
010Processor Flag 2
011Processor Flag 3
100Processor Flag 4
101Processor Flag 5
110Processor Flag 6
111Processor Flag 7

49:0

Reserved