Thanks to cccip's suggestion (
http://www.tonymacx86.com/graphics/...e-graphics-drivers-10-10-1-343-01-02-a-6.html ) I turned of graphics enabler ("No") and now the 970 is recognized.
I installed using yosemite 10.10.1 with the G1 970 plugged in and nv_disable=1 ;
ran multibeast (user dsdt);
installed the Nvidia drivers;
changed org.chameleon.Boot.plist and added "nvda_drv=1" to the following string:
<key>Kernel Flags</key>
<string>kext-dev-mode=1
nvda_drv=1</string>
And <key>GraphicsEnabler</key> to <string>No</string>
(TextEdit doesn't allow me to change the file, so I went to the terminal and did:
cd /extra
Sudo nano org.chameleon.Boot.plist)
Rebooted and now the video card is recognized. Except for the last part of the startup where I only see the loading bar. It works great!
During the Yosemite installation and during the first startup, the OS X video drivers make it stutter, it's a bit annoying and takes some patience, but it works.
I'm now working on getting my sound back. I installed the ALC 889, it recognizes when I plug in the jack, but no sound... I've repaired disk permissions but with no change...
So I'm back on the hunt
@justr : Sorry it wasn't clear in my post, but I installed the drivers when I booted using the USB stick, but on the fresh install. Did multibeast and then directly the Nvidia drivers
MEA CULPA: Sound works, I didn't realize that the "play feedback when volume is changed" is off... Feeling a bit
BUT