10 March 2003.  SMS.

      Macintosh Portable Internal SCSI Cable

   The adapter cable described in this document allows a normal SCSI
disk drive (with a normal, narrow SCSI, 50-pin connector) to be
connected to the 34-pin internal SCSI connector in a Macintosh Portable
computer.  It allows the original (40MB) disk drive to be replaced by a
more readily available (and higher capacity) drive.  Only a low-profile
drive will fit in the physical space, and the power requirement for the
replacement drive should be fairly close to that of the original drive,
to avoid damage to the power supply in the computer.

   For example, the power rating for the 80MB Quantum ProDrive ELS (5V
230mA, 12V 135mA) is lower than that of the original 40MB Apple Hard
Disk 40SC (Conner CP-3045, 5V 275mA, 12V 250mA).

   Normally, on the two-row 50-pin connector, odd pins 1-23 and 27-49
are ground, and pin 25 is not connected.  In this adapter cable, the
connections 2-47, 6-49, 11-39, and 16-5, are opportunistic grounds, easy
to make with paired conductors in the 34-conductor ribbon cable.

   Attach the 34-pin connector to the ribbon cable last, as this makes
it easier to get the cable length correct.


    SCSI    34-pin   50-pin

   TERMPWR    NC       26

   -REQ        1       48         \ pair
   (gnd)       2       47  (gnd)  /
   -MSG        3       42
   -C/D        4       46
   -I/O        5       50         \ pair
   (gnd)       6       49  (gnd)  /
   -ACK        7       38
   -ATN        8       32
   -BSY        9       36
   -RST       10       40         \ pair
   (gnd)      11       39  (gnd)  /
   -SEL       12       44
   -DB(P)     13       18
   -DB(0)     14        2
   -DB(1)     15        4         \ pair
   (gnd)      16        5  (gnd)  /
   -DB(2)     17        6
   -DB(3)     18        8
   -DB(4)     19       10
   -DB(5)     20       12
   -DB(6)     21       14
   -DB(7)     22       16

   5V pwr     23 -----+           12  0  0  5
   5V pwr     24 -----+          /------------\
   12V pwr    25 ---+ |         /              \
   12V pwr    26 ---+ |        |   o  o  o  o   |
   0V pwr     27 -+ | |        |                |
   0V pwr     28 -+ | |        +----------------+
   0V pwr     29 -+ | |            Y  B  B  R
   0V pwr     30 -+ | |
   12V pwr    31 ---+ |      Female power connector, as viewed
   12V pwr    32 ---+ |      from the disk drive.  (Typical wire
   5V pwr     33 -----+      colors are Yellow, Black, and Red.)
   5V pwr     34 -----+



   Signal lines in sequence for the 50-pin connector.

    SCSI    34-pin   50-pin

   -DB(0)     14        2
   -DB(1)     15        4         \ pair
   (gnd)      16        5  (gnd)  /
   -DB(2)     17        6
   -DB(3)     18        8
   -DB(4)     19       10
   -DB(5)     20       12
   -DB(6)     21       14
   -DB(7)     22       16
   -DB(P)     13       18
                       20  (gnd)
                       22  (gnd)
                       24  (gnd)
   TERMPWR             26
                       28  (gnd)
                       30  (gnd)
   -ATN        8       32
                       34  (gnd)
   -BSY        9       36
   -ACK        7       38
   (gnd)      11       39  (gnd)  \ pair
   -RST       10       40         /
   -MSG        3       42
   -SEL       12       44
   -C/D        4       46
   (gnd)       2       47  (gnd)  \ pair
   -REQ        1       48         /
   (gnd)       6       49  (gnd)  \ pair
   -I/O        5       50         /


   Change notice: In a previous version of this document, the connection
to pin 5 on the 50-pin connector was made to pin 3, instead.  The
function (ground) is the same, but using pin 5 makes the wire order a
bit nicer.