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       # WESTERN DIGITAL CORPORATION
       
          WD1004A-WX1 (REV. A)
       
          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
          
       
          +------------------------------------------------------------+
          |                        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       |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |                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  |
          |------------------------------------------------------------|
          |  Note: The function of W17-W20 & W25-W28 is unidentified.  |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |               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.           |
          +------------------------------------------------------------+