Intel Extensible Firmware Interface - Manual (Page 905)

32/64-Bit UNDI Specification
Version 1.10 12/01/02 E-39
NOTE
Additional requirements for S/W UNDI implementations: Processor register contents must be
unchanged by S/W UNDI command execution (the application/driver does not have to save
processor registers when calling S/W UNDI). Processor arithmetic flags are undefined
(application/driver must save processor arithmetic flags if needed). Application/driver must
remove CDB address from stack after control returns from S/W UNDI.
NOTE
Additional requirements for 32-bit network devices: All addresses given to the S/W UNDI must be
32-bit addresses. Any address that exceeds 32 bits (4 GB) will result in a return of one of the
following status codes: PXE_STATCODE_INVALID_PARAMETER,
PXE_STATCODE_INVALID_CDB or PXE_STATCODE_INVALID_CPB.
When executing linked commands, command execution will stop at the end of the CDB list (when
the
PXE_CONTROL_LINK bit is not set) or when a command returns an error status code.
E.4.1 Command Linking and Queuing
When linking commands, the CDBs must be stored consecutively in system memory without any
gaps in between. Do not set the Link bit in the last CDB in the list. As shown in Figure E-7, the
Link bit must be set in all other CDBs in the list.
OM13188
Linked CDBs
0x00
0x1F
0x20
0x3F
Set Link bit.
0x40
0x5F
Set Link bit.
Do not set
Link bit.
CDB
CDB
CDB
Figure E-7. Linked CDBs