Intel IA-32 - Manual (Page 433)

Vol. 3A 9-59
PROCESSOR MANAGEMENT AND INITIALIZATION
Figure 9-8. Microcode Update Write Operation Flow [1]
1
Valid Update
Header Version?
Loader Revision Match
BIOS’s Loader?
Does Update Match A
CPU in The System
Write Microcode Update
Does Update
Checksum Correctly?
Yes
Yes
Yes
No
Return
CPU_NOT_PRESENT
No
Return
INVALID_HEADER
No
Return
INVALID_HEADER
No
Return
INVALID_HEADER_CS