$ sudo hdparm --dco-identify /dev/sdb

/dev/sdb:
SG_IO: bad/missing sense data, sb[]:  70 00 05 00 00 00 00 0a 00 00 00 00 20 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
DCO Checksum FAILED!
DCO Revision: 0x0070 -- unknown, treating as 0002
The following features can be selectively disabled via DCO:
    Transfer modes:
         mdma0 mdma1 mdma2

    Real max sectors: 2561
    ATA command/feature sets:

$ sudo hdparm --dco-identify /dev/sdb

/dev/sdb:
SG_IO: bad/missing sense data, sb[]:  70 00 05 00 00 00 00 0a 00 00 00 00 24 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
DCO Checksum verified.
DCO Revision: 0x0000 -- unknown, treating as 0002
The following features can be selectively disabled via DCO:
    Transfer modes:

    Real max sectors: 1
    ATA command/feature sets:

$ sudo hdparm --yes-i-know-what-i-am-doing --dco-restore /dev/sdb

/dev/sdb:
 issuing DCO restore command
SG_IO: bad/missing sense data, sb[]:  70 00 05 00 00 00 00 0a 00 00 00 00 24 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

$ sudo hdparm --dco-identify /dev/sdb

/dev/sdb:
SG_IO: bad/missing sense data, sb[]:  70 00 05 00 00 00 00 0a 00 00 00 00 24 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
DCO Checksum FAILED!
DCO Revision: 0x0070 -- unknown, treating as 0002
The following features can be selectively disabled via DCO:
    Transfer modes:
         mdma0 mdma1 mdma2

    Real max sectors: 2561
    ATA command/feature sets:

$ sudo hdparm --dco-identify /dev/sda

/dev/sda:
DCO Checksum verified.
DCO Revision: 0x0002
The following features can be selectively disabled via DCO:
    Transfer modes:
         mdma0 mdma1 mdma2
         udma0 udma1 udma2 udma3 udma4 udma5 udma6
    Real max sectors: 500118192
    ATA command/feature sets:
         SMART self_test error_log security HPA 48_bit
         FUA selective_test write_read_verify
         WRITE_UNC_EXT
    SATA command/feature sets:
         NCQ interface_power_management SSP