Vol. 3A 9-29
PROCESSOR MANAGEMENT AND INITIALIZATION
Processor Signature
12
4
Extended family, extended model, type, family, model, and stepping
of processor that requires this particular update revision (e.g.,
00000650H). Each microcode update is designed specifically for a
given extended family, extended model, type, family, model, and
stepping of the processor.
The BIOS uses the processor signature field in conjunction with the
CPUID instruction to determine whether or not an update is
appropriate to load on a processor. The information encoded within
this field exactly corresponds to the bit representations returned by
the CPUID instruction.
Checksum
16
4
Checksum of Update Data and Header. Used to verify the integrity of
the update header and data. Checksum is correct when the
summation of all the DWORDs (including the extended Processor
Signature Table) that comprise the microcode update result in
00000000H.
Loader Revision
20
4
Version number of the loader program needed to correctly load this
update. The initial version is 00000001H.
Processor Flags
24
4
Platform type information is encoded in the lower 8 bits of this 4-
byte field. Each bit represents a particular platform type for a given
CPUID. The BIOS uses the processor flags field in conjunction with
the platform Id bits in MSR (17H) to determine whether or not an
update is appropriate to load on a processor. Multiple bits may be set
representing support for multiple platform IDs.
Data Size
28
4
Specifies the size of the encrypted data in bytes, and must be a
multiple of DWORDs. If this value is 00000000H, then the microcode
update encrypted data is 2000 bytes (or 500 DWORDs).
Total Size
32
4
Specifies the total size of the microcode update in bytes. It is the
summation of the header size, the encrypted data size and the size of
the optional extended signature table. This value is always a multiple
of 1024.
Reserved
36
12
Reserved fields for future expansion
Update Data
48
Data Size or
2000
Update data
Extended Signature
Count
Data Size + 48
4
Specifies the number of extended signature structures (Processor
Signature[n], processor flags[n] and checksum[n]) that exist in this
microcode update.
Extended Checksum
Data Size + 52
4
Checksum of update extended processor signature table. Used to
verify the integrity of the extended processor signature table.
Checksum is correct when the summation of the DWORDs that
comprise the extended processor signature table results in
00000000H.
Reserved
Data Size + 56
12
Reserved fields
Table 9-7. Microcode Update Field Definitions (Contd.)
Field Name
Offset (bytes)
Length
(bytes)
Description