< number of bustypes supported.
< list of supported bustypes.
< API entry point.
< makes 8-bit cksum zero.
< physical connector count lower byte.
< physical connector count upper byte.
< Implementation flags.
< sizeof(PXE_SW_UNDI).
< PXE_ROMID_MAJORVER.
< PXE_ROMID_MINORVER.
< PXE_ROMID_REV.
< PXE_ROMID_SIGNATURE.
< zero, not used.
< zero, not used.