Int 15 Fn D042  R - Intel Pentium Pro Bios Update - Write Bios Update Are  [-]

   AX = D042h
   BL = 01h
   ES:DI -> microcode update block (see #0457)
   CX,DX,SI = segments of three 64K scratchpad areas for BIOS use

Return: CF clear if successful
   CF set on error
   AH = status (see #0456)
   AL = OEM error (if AH is not 00h or 86h, otherwise undefined)
       00h successful

Notes: a microcode update may also be initiated by a WRMSR instruction
     with ECX=0079h, EDX=00000000h, and EAX=linear address of update
     block (see #0457)
   at least 32K stack space must be available when this function is called

See Also: AX=D042h/BL=00h,AX=D042h/BL=02h,AX=D042h/BL=03h,MSR 00000079h

(Table 0456)
Values for Pentium Pro BIOS update status:
 00h   successful
 86h   not implemented
 90h   unable to erase NVRAM device
 91h   unable to write to NVRAM device
 92h   unable to read storage
 93h   NVRAM is full
 94h   specified processor stepping is not present in system
 95h   invalid header or loader version
 96h   wrong checksum in header
 97h   processor rejected the update
 98h   the same or a more recent update is already stored
 99h   update block number was out of range

Format of Pentium Pro microcode update block:
Offset Size    Description (Table 0457)
 00h   DWORD   update header version number (currently 00000001h)
       FFFFFFFFh = unused block
 04h   DWORD   revision number of this microcode update
 08h   DWORD   update creation date, as BCD mmddyyyy (month,day,year)
 0Ch   DWORD   family/model/stepping of processor to which update applied
       (same value as returned by CPUID instruction)
 10h   DWORD   checksum (used to force sum of all 512 DWORDs of the update
       block to 00000000h)
 14h   DWORD   revision number of loader needed to install update
       (currently 00000001h)
 18h 24 BYTEs  reserved for future expansion
 30h 2000 BYTEs    encrypted microcode data

See Also: MSR 00000079h,OPCODE "CPUID"