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> How to set the outputs on nVidia boards, The NVCAP string (enable VGA, DVI, HDMI, TV ...)
post Feb 17 2009, 01:19 AM
Post #1
NVCAP exact working about display outputs has now been properly figured and automatic NVCAP creation is built inside NVEnabler.
This thread is outdated and is only kept here for record (because its content is not so wrong smile.gif)

Most nVidia cards have 2 channels with different physical connectors changing from one model to another. (VGA+DVI, dual DVI, dual VGA, single VGA, single DVI etc...)
By default the geforce driver doesn't know what kind of outputs are on your board, which means it could send a wrong signal.
Eg : It could send a DVI signal to your VGA output, or TV signal to VGA, which is obviously wrong, leading to black screen or various kinds of system hangs.

To correctly set the output format, the driver uses a string named NVCAP. This string allows apple to not restrict the driver to only one scheme of outputs, otherwise they'd have to recode a driver anytime it changes with a different model (what they do for ATI actually).
This string gives a kind of map to the driver, so it can know what kind of signal to send where.

To get good support, the NVCAP has to be set correctly in your graphic injecter plist.

I figured this using a 7600GS : VGA + DVI/VGA output

Here is a new template for most possible configurations :

[Pictures removed, content is now outdated]

I couldn't test DVI because I don't have a DVI display. Please test and report if it works.
Keep in mind that this is totally experimental and may (and probably does) contain errors.
I regularly update this thread, and the more I get feedback, the closer we get.

TV out only works randomly with Leopard. Fixed

Important rules :

- The logical channels (desktop #) must match the hardware channels (there are 2 heads). So, desktop #1 should be set on hardware channel 1.
To know what output is on what channel, boot windows with the 2 display outputs connected, click the button "identify displays", the big numbers will give you the channels currently used by the display (1 or 2). If someone knows a better way to find, the tip is welcome)
For TV it's more complicated because it varies with the board. Some have TV on channel 2, some on channel 1, and the windows method doesn't help because most boards can dynamicly change it, so the number is not fixed.

- You must boot with the correct primary output (eg : booting with VGA1 disconnected whereas it is set as primary [yellow] won't work nice)
Said simply : 1 yellow output MUST be plugged

- The primary display is considered fixed and should NOT be changed while computer is running.

- You can't use multiple displays on the same channel. eg : in the DVI+VGA template, it means you can use channel 2 for TV *or* DVI *or* VGA.
Plugging more than 1 display will cause weird behavior when detecting displays (very slow system + mouse).
Said simply : only 1 screen at time per color

[s]- Boot with TV out disconnected, otherwise it will hang on blue screen. (I have an idea to fix this, will check later).[/s] Fixed

[s]- When hot-plugging displays (only allowed on 2nd channel), you must 1st go back to single screen mode before switching.
eg : if your 2nd screen is currently DVI and you want to change to TV out : unplug DVI, redetect displays, plug TV, redetect displays.
Directly swapping will cause the same weird behavior as above.[/s] Fixed

- If you need a custom NVCAP, you can follow the same template but you can't mix stuff from different hardware channels.

- Values are not supposed to overlap each other for the 1st and secondary screen (you can't send 2 pictures to 1 output) hence, each value is supposed to be the exact negative of the other.

- It seems that people with dual DVI-board are going to have to choose between dual DVI and TV support. Both are possible, but not with the same NVCAP : the driver can't handle this. the nVidia boards on mac pro simply don't support TV out at all, however this can be hacked, sacrificing one of the DVIs, that sucks, blame apple.


- Dual VGA not well supported, you might have better results using older kexts.
More infos will come later with updates/corrections.

If you know the correct values for your board, posting it here is welcome. No need anymore

Don't forget the NVCAP only depends on the physical outputs of the board, don't consider things like memory size, or the plugged screen

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