Vol. 3A 9-31

PROCESSOR MANAGEMENT AND INITIALIZATION

9.11.2 

Optional Extended Signature Table

The extended signature table is a structure that may be appended to the end of the encrypted data when the 
encrypted data only supports a single processor signature (optional case). The extended signature table will always 
be present when the encrypted data supports multiple processor steppings and/or models (required case). 
The extended signature table consists of a 20-byte extended signature header structure, which contains the 
extended signature count, the extended processor signature table checksum, and 12 reserved bytes (Table 9-9). 
Following the extended signature header structure, the extended signature table contains 0-to-n extended 
processor signature structures.
Each processor signature structure consist of the processor signature, processor flags, and a checksum 
(Table 9-10). 
The extended signature count in the extended signature header structure indicates the number of processor signa-
ture structures that exist in the extended signature table.  
The extended processor signature table checksum is a checksum of all DWORDs that comprise the extended signa-
ture table. That includes the extended signature count, extended processor signature table checksum, 12 reserved 
bytes and the n processor signature structures. A valid extended signature table exists when the result of a 
DWORD checksum is 00000000H.

Update Data (Data Size bytes, or 2000 Bytes if Data Size = 00000000H)

48

Extended Signature Count ‘n’

Data Size + 

48

Extended Processor Signature Table Checksum

Data Size + 

52

Reserved (12 Bytes)

Data Size + 

56

Processor Signature[n] 

Data Size + 

68 + 

(n * 12)

Processor Flags[n]

Data Size + 

72 + 

(n * 12)

Checksum[n] 

Data Size + 

76 + 

(n * 12)

Table 9-9.  Extended Processor Signature Table Header Structure

Extended Signature Count ‘n’

Data Size + 48

Extended Processor Signature Table Checksum

Data Size + 52

Reserved (12 Bytes)

Data Size + 56

Table 9-10.  Processor Signature Structure 

Processor Signature[n] 

Data Size + 68 + (n * 12)

Processor Flags[n]

Data Size + 72 + (n * 12)

Checksum[n] 

Data Size + 76 + (n * 12)

Table 9-8.  Microcode Update Format (Contd.)

31

24

16

8

0

Bytes