INTERNAL SCSI DISK ...50 PIN CONNECTOR (A3000 MOTHERBOARD)
------------------------------------------------

   2    DATA 0             26   TERMINATION POWER
   4    DATA 1             28   GROUND
   6    DATA 2             30   GROUND
   8    DATA 3             32   ATN*
   10   DATA 4             34   N.C.
   12   DATA 5             36   BSY
   14   DATA 6             38   ACK*
   16   DATA 7             40   RST*
   18   PARITY             42   MSG*
   20   GROUND             44   SEL*
   22   GROUND             46   C/D
   24   GROUND             48   REQ*
                           50   I/O

(ALL ODD-NUMBERED PINS, EXCEPT PIN 25, ARE CONNECTED TO GROUND. PIN 25 IS
OPEN)

See the ANSI standard SCSI (Small Computer Standard Interface)
Specification for more information.