int i_NbrAiChannel;
        int i_NbrAiChannelDiff;
        int i_AiChannelList;
-       int i_NbrAoChannel;
        int i_AiMaxdata;
        unsigned char b_AvailableConvertUnit;
        unsigned int ui_MinAcquisitiontimeNs;
+       unsigned int has_ao:1;
        unsigned int has_dig_in:1;
        unsigned int has_dig_out:1;
        unsigned int has_ttl_io:1;
                .i_NbrAiChannel         = 16,
                .i_NbrAiChannelDiff     = 8,
                .i_AiChannelList        = 16,
-               .i_NbrAoChannel         = 4,
                .i_AiMaxdata            = 4095,
                .b_AvailableConvertUnit = 6,
                .ui_MinAcquisitiontimeNs = 10000,
+               .has_ao                 = 1,
                .has_ttl_io             = 1,
        },
        [BOARD_APCI3100_8_4] = {
                .i_NbrAiChannel         = 8,
                .i_NbrAiChannelDiff     = 4,
                .i_AiChannelList        = 8,
-               .i_NbrAoChannel         = 4,
                .i_AiMaxdata            = 4095,
                .b_AvailableConvertUnit = 6,
                .ui_MinAcquisitiontimeNs = 10000,
+               .has_ao                 = 1,
                .has_ttl_io             = 1,
        },
        [BOARD_APCI3106_16_4] = {
                .i_NbrAiChannel         = 16,
                .i_NbrAiChannelDiff     = 8,
                .i_AiChannelList        = 16,
-               .i_NbrAoChannel         = 4,
                .i_AiMaxdata            = 65535,
                .b_AvailableConvertUnit = 6,
                .ui_MinAcquisitiontimeNs = 10000,
+               .has_ao                 = 1,
                .has_ttl_io             = 1,
        },
        [BOARD_APCI3106_8_4] = {
                .i_NbrAiChannel         = 8,
                .i_NbrAiChannelDiff     = 4,
                .i_AiChannelList        = 8,
-               .i_NbrAoChannel         = 4,
                .i_AiMaxdata            = 65535,
                .b_AvailableConvertUnit = 6,
                .ui_MinAcquisitiontimeNs = 10000,
+               .has_ao                 = 1,
                .has_ttl_io             = 1,
        },
        [BOARD_APCI3110_16_4] = {
                .i_NbrAiChannel         = 16,
                .i_NbrAiChannelDiff     = 8,
                .i_AiChannelList        = 16,
-               .i_NbrAoChannel         = 4,
                .i_AiMaxdata            = 4095,
                .b_AvailableConvertUnit = 6,
                .ui_MinAcquisitiontimeNs = 5000,
+               .has_ao                 = 1,
                .has_dig_in             = 1,
                .has_dig_out            = 1,
                .has_ttl_io             = 1,
                .i_NbrAiChannel         = 8,
                .i_NbrAiChannelDiff     = 4,
                .i_AiChannelList        = 8,
-               .i_NbrAoChannel         = 4,
                .i_AiMaxdata            = 4095,
                .b_AvailableConvertUnit = 6,
                .ui_MinAcquisitiontimeNs = 5000,
+               .has_ao                 = 1,
                .has_dig_in             = 1,
                .has_dig_out            = 1,
                .has_ttl_io             = 1,
                .i_NbrAiChannel         = 16,
                .i_NbrAiChannelDiff     = 8,
                .i_AiChannelList        = 16,
-               .i_NbrAoChannel         = 4,
                .i_AiMaxdata            = 65535,
                .b_AvailableConvertUnit = 6,
                .ui_MinAcquisitiontimeNs = 5000,
+               .has_ao                 = 1,
                .has_dig_in             = 1,
                .has_dig_out            = 1,
                .has_ttl_io             = 1,
                .i_NbrAiChannel         = 8,
                .i_NbrAiChannelDiff     = 4,
                .i_AiChannelList        = 8,
-               .i_NbrAoChannel         = 4,
                .i_AiMaxdata            = 65535,
                .b_AvailableConvertUnit = 6,
                .ui_MinAcquisitiontimeNs = 5000,
+               .has_ao                 = 1,
                .has_dig_in             = 1,
                .has_dig_out            = 1,
                .has_ttl_io             = 1,
        },
        [BOARD_APCI3500] = {
                .pc_DriverName          = "apci3500",
-               .i_NbrAoChannel         = 4,
+               .has_ao                 = 1,
                .has_ttl_io             = 1,
        },
 };
 
        /*  Allocate and Initialise AO Subdevice Structures */
        s = &dev->subdevices[1];
-       if (board->i_NbrAoChannel) {
+       if (board->has_ao) {
                s->type = COMEDI_SUBD_AO;
                s->subdev_flags = SDF_WRITEABLE | SDF_GROUND | SDF_COMMON;
-               s->n_chan = board->i_NbrAoChannel;
+               s->n_chan = 4;
                s->maxdata = 0x0fff;
                s->range_table = &apci3xxx_ao_range;
                s->insn_write = i_APCI3XXX_InsnWriteAnalogOutput;