Intel 64 and IA-32 Architectures Software Developers Manual Volume 3A, System Programming Guide, Part 1

Vol. 3A 9-61
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
Ret ur n
CPU_NOT_PRESENT
N
o
Ret ur n
INVALID_HEADER
No
Ret ur n
INVALID_HEADER
N
o
Ret ur n
INVALID_H EA DER_ CS