Hi all,

First of all, _always_ search the information at the place where it must be.
Never beleive information on a "a friend of mine told me..." basis !

a. Determining the pin numbering sheme.
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So, how can I know the pin number of a connector on a Macintosh Main Logic Board ?

Very simple, take a magnifying glass and have a look at the video port on the
Macintosh Main Logic Board (on the rear of the computer). Then you can see the
pin numbers...

b. What are the video sense codes ?
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The video sense codes are here to let the video card or in-board video what kind
of monitor is plugged so they know what kind of video signal they have to give.
This let the video card or in-board video know if you have a 12" color /
monochrome or whatever supported monitor you have connected and generate the
appropriate video. (512 * 384, 640 * 480, etc., Pal, Secam, NTSC, etc.)

There is two different video sense codes: Standard Sense Codes and Extended
Sense Codes.

To know more about this, you have to go to the Apple Documentation:

HW08-Color Monitor Connections
HW26-Mac Quadra Built-In Video
HW 30 - Sense Lines

there may be other document that describe these.

Basically, pins 4, 7 and 10 are involved and in “HW 30 - Sense Lines” they talk
about make a strap from one or many of the three pins to the ground; they also
talk about the use of a diode.

Other information can be found in the Developer’s Note (Hardware pdf files);
some are available on-line:

<http://developer.apple.com/techpubs/hardware/Developer_Notes/Macintosh_CPUs-68K_Desktop/>

For the happy few that have the “DeveloperCD Series” (From Apple Developer
Group), take one Reference Library CD and you have the right documentation handly.

Example of path:

Dev.CD Sep 95 RL:Macintosh Technical Notes:Hardware:   for the Macintosh
Technical Notes
Dev.CD Sep 95 RL:Developer Notes:                      for the Macintosh
Hardware Notes (CPU, Peripherals and Printers)

There’s even a “Display Device Driver Guide” in the “Dev.CD Sep 95 RL:Developer
Notes:” folder.

Yes, “Sep 95” means September 1995, “RL” = Reference Library:


Taken from “HW 30 - Sense Lines”

Sense Lines
The sense line protocol was implemented when Apple recognized the need for a
mechanism that would allow a display card to identify the monitor connected to
it. For example, the built-in video display circuitry on CPUs such as the
Macintosh Quadras and the PowerBook 160 and 165c can configure itself according
to the monitor that is connected at boot time. The identification scheme works
fine, but there is one problem. There are only three sense lines and this limits
the number of different monitors to seven plus the no-connect case. To overcome
this limitation, newer display cards and built-in video use extensions to the
sense line scheme that allow for new codes.


Emile


PS: If I wasn’t clear enough, feel free to ask me and remember I’m just a French
guy so sometimes my English is ... Frenglish !