| 80 Wire IDE Connector Information:IDE Hard Disk * 40 pin / 80 wire header  The following explanation provided to us from George
      Walker, BuildOrBuy Member. 
        
          | 1 | reset |  | 2 | ground | 
              On the 80 wire connectors,
              the following pins measured as common: 2, 19, 22, 24, 26, 30, and
              40 (Motherboard, Gray and Black).
              On the connector that connects to
              the Motherboard pin # 34 does not connect to the ribbon cable but
              is connected to common. Some cables have a hole in the cable as a
              way of disconnecting pin # 34 from the other two connectors.On the middle (Gray) connector pin
              #28 is not connected to the ribbon cable. (C/S Slave). The extra 40 wires, one of which
              is inserted between each data wire, are all connected in common
              and are connected with 2, 19, 22 etc. on each connector.On most IDE connectors on
              Hard drives and CD-ROM Drives, Pin 20
              is missing. |  
          | 3 | data
            7 | 4 | data
            8 |  
          | 5 | data
            6 | 6 | data
            9 |  
          | 7 | data
            5 | 8 | data
            10 |  
          | 9 | data
            4 | 10 | data
            12 |  
          | 11 | data
            3 | 12 | data
            13 |  
          | 13 | data
            2 | 14 | data
            14 |  
          | 15 | data
            1 | 16 | data
            15 |  
          | 17 | data
            0 | 18 | n/c |  
          | 19 | ground | 20 | ground |  
          | 21 | n\c | 22 | ground |  
          | 23 | iow | 24 | ground |  
          | 25 | ior | 26 | bale |  
          | 27 | n\c | 28 | ground |  
          | 29 | n\c | 30 | n\c |  
          | 31 | idint | 32 | n\c |  
          | 33 | sa1 | 34 | n\c |  
          | 35 | sa0 | 36 | sa2 |  
          | 37 | cs5 | 38 | hcs1 |  
          | 39 | n\c | 40 | n\c |  
        www.pcguide.com/ref/hdd/if/ide/conf_Cable80.htm
           Plextor
          University - 80-Conductor ULTRA ATA Cable: 80 Wire / 40 Pin |