IBM 560 - Manual (Page 68)

Header Image
Systems that support SMAPI BIOS must provide the following header
image in the F000 segment system ROM area at the 16-byte
boundary. The client needs to search and find this SMAPI BIOS
header image to get the entry point for the service.
Field Offset Length Value
Signature 00h 4 bytes ' $SMB ' (ASCII)
Version (Major) 04h Byte 01h
Version (Minor) 05h Byte 00h
Length 06h Byte 20h
Checksum 07h Byte –
Information Word 08h Word –
Reserved 1 0Ah Word –
Real mode 16-bit offset to entry
point 0Ch Word –
Real mode 16-bit code segment
address 0Eh Word –
Reserved 2 10h Word –
16-bit protected mode offset to
entry point 12h Word –
16-bit protected mode code
segment base address 14h Dword –
32-bit protected mode offset to
entry point 18h Dword –
32-bit protected mode code
segment base address 1Ch Dword –
Signature ASCII Code ' $SMB ' is stored at the top of the header
image.
Version (Major/Minor)
Indicates the SMAPI BIOS version.
Length The length of the header image.
Checksum Checksum byte area. The client verifies that this
header image is valid by using this checksum; the client
should check all header image bytes, and the result will
be zero bytes.
A-4 ThinkPad 560/560E SMAPI BIOS