In reference to my previous entry about getting an SGI monitor to work with Mac OS X I received a note from Ed on the comp.sys.sgi.misc newsgroup. Here’s what he had to say:
“That monitor only works with sync-on-green. IF you can use another monitor to manually force the Mac into an old Mac mode, 1152 x 870 @75HZ, it MAY also generate the old mac sync-on-green. Not too likely, but a remote possibility. The monitor can also be modified internally to connect the H & V sync leads out to the 13W3 connector. (The wires are not physically connected, but the sync circuits are on the board internally) Google for info, but be aware that a LOT of misinformation exists on this subject. A good monitor repair shop should be able to make the mod work, for a price. Another problem if you take this approach is that the sgi 13W3 cables also don’t connect the sync lines through the cable. So you will need a different adapter that will plug into the 13W3 connector on the monitor and use a high quality male to male VGA (HD15) cable. You will need to make sure the adapter connects the sync lines to the same pins as are connected to the 13W3 connector on the monitor by the mod shop. An even better alternative is to donate or dump that monitor and get a newer one. It has scan range limitations and is already 10 years old, who knows how many hours it has on it. You may go to a lot of trouble and expense to find out that the monitor is ready to die anyway… If it were me, I would try setting the mode on the Mac, if that didn’t work, I would get a different monitor that will work with the sync-on-green from the sgi’s and also work with separate syncs for the mac. Good luck.”
— Ed (the cable geek)