Resolved GTX 960 on 10.10.0 Mac Pro 2,1 will not boot

[Jacob William Turnbill]

Hey all,

This is my first new post on this forum. It seems like a great community and I'm having a heck of a time getting this GPU to work. Here is my scenario:

My system is a Mac Pro 2,1 with:

OSX 10.10.0(thanks Pike!)
2x Quad Core Xeon 3.0GHZ processors
32GB 667 RAM
128GB SSD
750GB 7200RPM HDD
3TB 7200RPM HDD

I followed all instructions in the sticky at the top of this forum and am not able to get my Mac to boot to the login screen. I hear the chime, but no output is sent from the GPU. Below is what I have tried:

I installed the Web and CUDA drivers while my old Radeon HD 6850 was being used for output. I set flags appropriately before and after installs. I shut down, put in the GTX, and no output upon boot.

I went to the nVidia settings in System Preferences and set the driver to nVidia instead of Apple while using my Radeon 6850. I shut down, put in the GTX, and no output upon boot.

I plugged in the stock Radeon card into the bottom PCI slot and the GTX into slot 3. The Radeon was properly identified, but the GTX was identified as a 256MB VRAM card.

My Mac Pro only has one six pin connector; for now, I've plugged this in to one of the Y 6 pin to 8 pin connectors, and then into the GTX. I have ordered a standard 6 pin to 8 pin connector(NOT A Y CABLE LIKE WHAT CAME WITH THE GTX). Will this resolve my issue, or is this related at all? My understanding is that one 6 pin connector delivers 75W and the PCI-e 1.0 will deliver 75W, for a total of 150W, which should be enough for this card.

I am at my wit's end and I really want to get this working, as it is the last piece to the major upgrades I've made to my Mac Pro. Any help will be extremely appreciated. Thank you!

EDIT: Just to clarify: I am ok with the lack of Boot Screens with this card. The issue is that the login window never appears and I am not able to access my system due to the complete lack of video output with the GTX 960. Thanks!

 

[MacVidCards]

Try using other side of the Y

 

[Jacob William Turnbill]

I've tried both sides.

Additionally, the fans do spin up on the card and it is recognized in OSX, but as a generic nVidia card with only 256MB of VRAM.

I would think that even with the lack of power, the card should at least output a downgraded video quality/unaccelerated desktop. Am I incorrect in this thought process? Any other ideas?

EDIT: I have tried one of the DP ports and the DVI port, but to no avail. Any reports of only specific ports working on this card with OS X Yosemite on a 2,1(or other unsupported Mac)? I am ok with even just one of the outputs working.

 

[MacVidCards]

No, without OS drivers and no EFI there would be nothing. Using your ATI card verify that Web drivers are loaded. With both cards in check extensions and see which nvidia ones are loaded

 

[Jacob William Turnbill]

Ok, so last night I tried both sides of the Y connector again. Success! After not booting up with the first side of the Y, the second side did work! Thanks so much, you're a lifesaver.