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       # WESTERN DIGITAL CORPORATION
       
          WD1004A-WX1
       
          Data bus: 8-bit, PC/AT, PC/AT
       
          Size: Half-length, full-height card
       
          Hard drives supported:  Two MFM ST506/412 drives
       
          Floppy drives supported: None
       
          Maximum heads/cyl.: 16 heads and 1024 cylinders
       
   IMG IMG 1
          
       
          +------------------------------------------------------------+
          |                USERS CONFIGURABLE SETTINGS                 |
          |------------------------------------------------------------|
          |               Function                | Location | Setting |
          |---------------------------------------+----------+---------|
          | » | Hard drive Interrupt request is   |   W27    | closed  |
          |   | IRQ5                              |          |         |
          |---+-----------------------------------+----------+---------|
          |   | Hard drive Interrupt request is   |   W27    |  open   |
          |   | IRQ2                              |          |         |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |                        CONNECTIONS                         |
          |------------------------------------------------------------|
          |                 Function                  |    Location    |
          |-------------------------------------------+----------------|
          | 34-pin control cable connector-hard drive |       J1       |
          |-------------------------------------------+----------------|
          | 20-pin data cable connector-drive 0       |       J2       |
          |-------------------------------------------+----------------|
          | 20-pin data cable connector-drive 1       |       J3       |
          |-------------------------------------------+----------------|
          | 5-pin connector-DC power                  |       J4       |
          |-------------------------------------------+----------------|
          | 4-pin connector-drive active LED          |       J5       |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |         BIOS DRIVE TYPE TABLE - (WD1004-27X ONLY)          |
          |------------------------------------------------------------|
          | Table # |  W17  |  W18  |  W19  |  W20  |Cap. |Hds. |Cyls. |
          |---------+-------+-------+-------+-------+-----+-----+------|
          |   |  0  |closed |closed |closed |closed |21MB |  4  | 612  |
          |---+-----+-------+-------+-------+-------+-----+-----+------|
          |   |  1  | open  |closed | open  |closed |10MB |  4  | 306  |
          |---+-----+-------+-------+-------+-------+-----+-----+------|
          |   |  2  |closed | open  |closed | open  |10MB |  2  | 615  |
          |---+-----+-------+-------+-------+-------+-----+-----+------|
          |»  |  3  | open  | open  | open  | open  |21MB |  4  | 615  |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |                I/O PORT & BIOS ADDRESS                 |
          |------------------------------------------------------------|
          |  I/O Port Address   | BIOS Address  |    W21    |   W22    |
          |---------------------+---------------+-----------+----------|
          | »   |   320-323h    | C8000-C9FFFh  |   open    |   open   |
          |-----+---------------+---------------+-----------+----------|
          |     |   324-327h    | CA000-CBFFFh  |  closed   |   open   |
          |-----+---------------+---------------+-----------+----------|
          |     |   328-32Bh    | CC000-CDFFFh  |   open    |  closed  |
          |-----+---------------+---------------+-----------+----------|
          |     |   32C-32Fh    | CE000-CFFFFh  |  closed   |  closed  |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |               MISCELLANEOUS TECHNICAL NOTES                |
          |------------------------------------------------------------|
          |  This controller has a built-in low-level format program.  |
          |  To enter the program run the DEBUG utility supplied with  |
          |           DOS and at the prompt enter: G=C800:5.           |
          |                                                            |
          |  If the system is not compatible with the Western Digital  |
          |  BIOS, a resistor must be installed at R23 to disable the  |
          |                          WD BIOS                           |
          +------------------------------------------------------------+