Power Macintosh Pinouts

This article presents the pinouts for non-AV Power Macintosh models. These pinouts include: ADB, GeoPort, SCSI, a floppy disk drive, built-in Ethernet, high-quality 16-bit stereo sound, and various levels of monitor support up to 21 inches, depending on the model.
Apple Desktop Bus (ADB)
-----------------------

One connector is located on the back panel of Power Macintosh computers.

It is a 4-pin mini-DIN socket.


Pin    Description
---    -----------

1     Data; grounded by an open collector or pulled to +5 V through 470
2     Power on, fed by +5 V through 100 k; connect to pin 4 to turn on
      the system
3     +5 V at 500 mA maximum drain; protected by a 1.25-A circuit breaker
4     Ground return


Ethernet
--------

All models of Power Macintosh contain built-in Ethernet.


Pin     Signal Name       Signal Description
----    --------------    ---------------------------------

1      FN Pwr            Power (+12V @ 2.1W or +5V @ 1.9W)
2      DI-A              Data In circuit A
3      DI-B              Data In circuit B
4      VCC               Voltage Common
5      CI-A              Control In circuit A
6      CI-B              Control In circuit B
7      +5V               +5 volts (from host)
8      +5V               Secondary +5 volts (from host)
9      DO-A              Data Out circuit A
10      DO-B              Data Out circuit B
11      VCC               Secondary Voltage Common
12      NC                Reserved
13      NC                Reserved
14      FN Pwr            Secondary +12V @ 2.1W or +5V @ 1.9W
Shell   Protective Gnd    Protective Ground



Serial Ports
------------

The back panel of all Power Macintosh models contain two I/O ports for serial telecommunication data.  Both sockets accept 9-pin plugs allowing either port to be independently programmed for asynchronous or synchronous communication formats up to 9600 bps.  This includes AppleTalk and the full range of Apple GeoPort protocols.


Pin    Name                  Function
---    ----                  --------

1     SCLK(out)             Reset pod or get pod attention
2     Sync(in)/SCLK(in)     Serial clock from pod (up to 920 Kbit/sec.)
3     TxD-                  Transmit -
4     Gnd/shield            Ground
5     RxD-                  Receive -
6     TxD+                  Transmit +
7     Wakeup/TxHS           Wake up CPU or do DMA handshake
8     RxD+                  Receive +
9     +5 V                  Power to pod (350 mA maximum)


SCSI Connection
---------------

The SCSI interface in Power Macintosh computers exists in two forms: an internal 50-pin ribbon connector for internal devices and an external DB-25 connector for external devices.


   Pin Number        Description          Pin Number        Description
-------------------   -----------      -------------------   -----------

Internal   External                    Internal   External
  1          7       Ground              2          8       /DATA0*
  3          9       Ground              4         21       /DATA1
  5         14       Ground              6         22       /DATA2
  7         16       Ground              8         10       /DATA3
  9         18       Ground             10         23       /DATA4
 11         24       Ground             12         11       /DATA5
 13                  Ground             14         12       /DATA6
 15                  Ground             16         13       /DATA7
 17                  Ground             18         20       /DATAP
 19                  Ground             20                  No connection
 21                  Ground             22                  No connection
 23                  Ground             24                  No connection
 25                  No connection      26         25       TERMPWR
 27                  Ground             28                  No connection
 29                  Ground             30                  No connection
 31                  Ground             32         17       /ATN
 33                  Ground             34                  No connection
 35                  Ground             36          6       /BUSY
 37                  Ground             38          5       /ACK
 39                  Ground             40          4       /RST
 41                  Ground             42          2       /MSG
 43                  Ground             44         19       /SEL
 45                  Ground             46         15       /C/D
 47                  Ground             48          1       /REQ
 49                  Ground             50          3       /I/O


* A slash (/) before a signal name indicates that it is in the low state when active.


Floppy Disk Drive Connection
----------------------------

All Power Macintosh models contain one internal Apple superDrive floppy disk drive, which supports GCR and MFM formats for 1.44 MB disks.

Pin   Signal   Description              Pin   Signal   Description
---   ------   -----------              ---   ------   -----------

 1   GND      Ground                    11   +5 V     +5 V
 2   PH0      Phase 0 state control     12   SEL      Head select
 3   GND      Ground                    13   +12 V    +12 V
 4   PH1      Phase 1 state control     14   /ENBL*   Drive enable
 5   GND      Ground                    15   +12 V    +12 V
 6   PH2      Phase 2 state control     16   RD       Read data
 7   GND      Ground                    17   +12 V    +12 V
 8   PH3      Phase 3 register write    18   WR       Write data
              strobe
 9   NC       No connection             19   +12 V    +12 V
10   /WRREQ   Write data request        20   NC       No connection


* A slash (/) before a signal name indicates that it is in the low state when active.


AudioVision Monitor Support
---------------------------

The Power Macintosh computers provide connection to AudioVision (and other
monitors when used with an adapter cable) by means of an AudioVision HDI-45
monitor socket on their back panel.


Pin   Description                  Pin   Description
---   -----------                  ---   -----------

 1   Analog audio ground           24   Reserved
 2   Audio input shield            25   Reserved
 3   Left channel audio input      26   Red ground (shield)
 4   Right channel audio input     27   Red video output (75 )
 5   Left channel audio output     28   I^2C data signal* (I-squared)
 6   Right channel audio output    29   I^2C clock signal* (I-squared)
 7   Reserved                      30   Reserved
 8   Monitor ID sense line 1**     31   Monitor ID
 9   Monitor ID sense line 2**     32   Monitor ID
10   Green ground (shield)         33   Vertical sync signal
11   Green video output (75 )      34   Composite sync signal
12   Video input power ground      35   ADB power +5 V
13   Power for camera +5 V         36   ADB ground
14   Reserved                      37   ADB data
15   Reserved                      38   Keyboard switch
16   Reserved                      39   Reserved
17   Reserved                      40   Reserved
18   Monitor ID sense line 3**     41   Monitor ID
19   S-video input shield          42   Horizontal sync signal
20   S-video input luminance (Y)   43   Video sync ground
21   S-video input chroma (C)      44   Blue ground (shield)
22   Reserved                      45   Blue video output (75 )


* Philips serial bus interface
** See Apple Technical Note 326


VRAM Expansion Cards
--------------------

VRAM expansion cards are Apple cards that plug into the PDS slots of Power Macintosh 7100/66 and 8100/88 computers.  They provide an additional DB-15 monitor output.

Pin   Description                  Pin   Description
---   -----------                  ---   -----------
 1   Red ground                     9   Blue video signal
 2   Red video signal              10   Monitor sense 2
 3   Composite synchronization     11   Synchronization ground
 4   Monitor sense 0               12   Vertical synchronization
 5   Green video signal            13   Blue ground
 6   Green ground                  14   Horizontal synchronization ground
 7   Monitor sense 1               15   Horizontal synchronization
 8   No connection


Sound I/O
---------

All Power Macintosh computers contain external stereo mini phone jacks for sound I/O, connected through amplifiers to the AWAC chip.


Panel label      Description
-----------      -----------

Audio In         8 k impedance, 2 V rms maximum, 22.5 dB gain available
Audio Line Out   37  impedance, 0.9 V rms maximum, attenuated -22,5 dB
                (crosstalk degrades from -80 to -32 dB when the audio
                 output is connectedto 32  headphones)


S-Video
-------

Power Macintosh AV Models include S-Video In/Out jacks.


NOTE: Non-AV Power Macintosh models do not include these S-Video In/Out jacks.


Pin    Input Connector          Output Connector
---

1      AGND                     AGND
2      AGND                     AGND
3      Video Y (luminance)      Video Y (luminance)
4      Video C (chroma)         Viceo C (chroma)
5      I^2C clock (I-squared)*  Composite Video
6      +12V at 250 mA maximum   No connection
7      1^2C data*               No connection


* Phillips serial bus

The following Tech Info Library article can help you find the Tech Note mentioned here:

Article 24493: "Apple Tech Notes: What They Are, Where To Find Them"
Published Date: Feb 19, 2012