When I enter System Preferences and select Displays, I am given a button to direct OS X to Detect Displays. But when I choose the button, nothing seems to happen. There are only two tabs visible--Display and Color--neither of which has anything to do with getting the software to recognize that a second cable has been
Mac OS X (10.6.8)
That is because a second display has NOT been seen. Check
About This Mac > More Info > Graphics & Displays ...
to see if anything at all is there:
What graphics card do yo have?
How is the good monitor connected?
How is the projector connected?
Does the projector work if you disconnect the other monitor?
Does the projector work with that input on another device?
When going through System Preferences, Displays, It clearly lists my monitor connected with a DVI cable on Port 1. But it does not see my projector which is connected via SVGA cable connected to the second port via a SVGA-DVI adapter. Now here's the kicker. When I open Bootcamp and operate with Windows 7 it sees both my monitor and the projector and operates just fine. This causes me to believe that there is nothing wrong with the graphics card. It also causes me to believe that there is nothing wrong with the cable connections. I switch back to OS X and then only the monitor works. My graphics card is NVIDIA Gforce 8800 GT.
The Mac uses a highly parameterized driver. It sets the parameters based on the response it receives from the display on the secondary EDID channel. That response lists the display's NAME (which is why it can be shown in system configuration displays) and its capabilities.
If your adapter does not pass the EDID signals, or the projector does not provide them, your projector will stay dark. Are you using a reputable adapter? These are the signals on a DVI port -- VGA is in the pins around the blade at the end plus one more form the top row of the grid (salmon pink in the diagram). EDID are in the adjacent pins (light blue):
graphic courtesy Wikipedia
The reason you may get a picture in Windows is that it does none of that. You generally set the resolution in a Control Panel, and it takes your word for it and outputs whatever you said, even if that damages your display.
| A female DE15 socket (videocard side). | |||
| Pin 1 | RED | Red video | |
|---|---|---|---|
| Pin 2 | GREEN | Green video | |
| Pin 3 | BLUE | Blue video | |
| Pin 4 | ID2/RES | formerly Monitor ID bit 2, reserved since E-DDC | |
| Pin 5 | GND | Ground (HSync) | |
| Pin 6 | RED_RTN | Red return | |
| Pin 7 | GREEN_RTN | Green return | |
| Pin 8 | BLUE_RTN | Blue return | |
| Pin 9 | KEY/PWR | formerly key, now +5V DC | |
| Pin 10 | GND | Ground (VSync, DDC) | |
| Pin 11 | ID0/RES | formerly Monitor ID bit 0, reserved since E-DDC | |
| Pin 12 | ID1/SDA | formerly Monitor ID bit 1, I²C data since DDC2 | |
| Pin 13 | HSync | Horizontal sync | |
| Pin 14 | VSync | Vertical sync | |
| Pin 15 | ID3/SCL | formerly Monitor ID bit 3, I²C clock since DDC2 | |
| The image and table detail the 15-pin VESA DDC2/E-DDC connector; the diagram’s pin numbering is that of a female connector functioning as the graphics adapter output. In the male connector, this pin numbering corresponds with the mirror image of the cable’s wire-and-solder side. | |||
at least some of pins 4, 10,11, 12, and 15 should be connected to pass EDID data through.
I realized that, from my second DVI port, I was actually trying to connect to my projector AND a second monitor via a splitter. Is there no way to get the video card to recognize the splitter?
Based on the previous replies the Mac does not know how to receive the identifying signals from the two monitors when they are connected with a splitter.
What not connect them to different ports on the graphics card?.
The only effective way to use a splitter on your Mac is to connect two essentially identical displays. Trying to support a VGA and a DVI off one output port will not work.
I'm having trouble using multiple displays on Mac Pro 2006 (OS X 10.6.8). System Preferences does not detect my projector. Suggestions?
