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Re: running without display on Mac hardware

(T)echnical (I)nfo (L)ibrary at Apple is the central repository for information about Apple's legacy (no longer produced) products. The Technical Information Library is essentially an archive of the reference database that was used by Apple's Telephone support staff. It's also the first place you should look when dealing with legacy stuff from Apple. It really does have most of the answers... from a macintosh user's viewpoint.
(So you'll have to think differently)

If you go to          til.info.apple.com
you can search the archives.
A quick search with         sense codes
returned several sources, such as

Searches in the til for things like
monitor configuration
will also get you the information you seek.

For those searching mail-archives and hoping to find all the answers in one place, I will spell it out for you below . . . keep the above message & links, you'll need them.

How to make a Mac boot without a monitor.
- - Running your Mac 'headless'
- - Wiring a Macintosh Video Cable

Unlike all other computers, to configure mac video: you plug the monitor into the computer and turn them on. No software drivers, switch settings, or fiddling of any kind are required. The monitor does not need autosensing. No kidding. Just plug a monitor(RGB, NTSC, PAL) of any resolution into the back of the mac and turn them on. There will be a quiz later, so test your memory now.

Macs are able to sense an individual monitor's characteristics by looking at a few special wires known as sense lines. These wires are unique to the Macintosh Computer. The mac 15pin port has a different shape than VGA cables. But it's those additional 'sense' wires that are the real difference.

The mac needs to know what kind of video setup to configure or it will halt the boot process. It gets this info by looking down those sense lines. If you wire only the sense lines, you can simulate a monitor and therefore complete the MacOS' startup process. The link above is to a document with tables listing many monitor configurations. Pick one** and review which sense wires need to be connected to specify its configuration.

Obtain a 15pin male cable end and some spare wire. RadioShack is rumoured to stock them. Insert only the sense code pins. You won't need the video signal(no monitor). Wire the plug to match the sense codes of the monitor you are "pretending" to connect to the mac.

    to configure the mac to run without a monitor, you
"Plug your new 'headless' mac adapter into the back of the mac and ___ ____ ___."

    **I will not suggest that you emulate the monitor
that will probably end up plugged into this mac
should it need maintenance.  ;)

    ***Nor will I recommend that you choose
the lowest possible resolution, colors, and
refresh rate as to reduce the
unused video system's footprint.
(On some Mac models, the video system can steal from system memory)
( I don't know if this is relevant to the Linux kernel once running)

I think that's about all. Did I forget anything?

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