BD_SBF
bd->offset[3] |= cpu_to_le32(BD_SBF);
dword3 |= BD_SOT|BD_SBF|(tfs<<BD_TFS_SHIFT);
bd->offset[3] = cpu_to_le32(BD_SBF);
bd->offset[3] &= cpu_to_le32(~BD_SBF);