2x 1080ti Black screen on Boot

[matakus]

So i had a titan X maxwell and a 1080ti working fine in OSX sierra 10.12.4 with the web drivers. for whatever reason, the titan X had a hardware failure and died. I replaced it with another 1080ti so now i have 2. Now i can only get a black screen with 2 1080tis installed. Doesnt matter which slot etc, just goes to a black screen. If i leave either plugged in by itself, the system boots showing a 1080ti installed. Windows see's both cards fine. Im using 6.1 but all other system's do the same thing (5.1, 14.2 etc)

I have tried all things, AGDPfix.app 1.3 and have injected each GPU seperately so they are seen both as GFX1x0 in IOreg as according to this guide https://www.tonymacx86.com/threads/ssdt-gpu-graphics-card-injection.183354/#post-1197682

Still no dice. I did a fresh install of 10.12.5 thinking that would solve the issue. Nope same thing. Again, i tried all the above steps on the new OS and same results.

Motherboard is an Asus Deluxe II, but i get the same results on the Asus Deluxe as well so clearly it's not hardware related. No other PCI cards are installed. Obviously doing all these tests took a bit of time, so now it's time to see if anyone else out there has had this issue or has a potential solution?

 

[tomkz]

have you tried using just the first display port on the card with just one monitor? (the one furthest away from the hdmi port...)

Edit:
NM.... you said you tried them all. Apologies.

Edit 2:
I just added a second 1080ti, and had some black screens at the beginning... I think that using the port I mentioned resolved it... that said, I do recall turning the default display to IG as i was also experimenting with finding the best way to split up my three monitors... (lowest temps) I'm not currently using the IG... but on the off chance that was a factor, thought I'd mention it.

I also had some weirdness where the final bootup changed from my middle monitor to my left... and only the left. The right had no signal, and the middle had the last part of the verbose log...

I'm using 10.12.5, 14,2, my mobo is a z170xp-sli...

 

[matakus]

have you tried using just the first display port on the card with just one monitor? (the one furthest away from the hdmi port...)

Edit:
NM.... you said you tried them all. Apologies.

Edit 2:
I just added a second 1080ti, and had some black screens at the beginning... I think that using the port I mentioned resolved it... that said, I do recall turning the default display to IG as i was also experimenting with finding the best way to split up my three monitors... (lowest temps) I'm not currently using the IG... but on the off chance that was a factor, thought I'd mention it.

I also had some weirdness where the final bootup changed from my middle monitor to my left... and only the left. The right had no signal, and the middle had the last part of the verbose log...

I'm using 10.12.5, 14,2, my mobo is a z170xp-sli...

So you have 2 1080tis booting ok?

Even if I plug in 1 monitor, that port, its just black. Really weird as just one works as expected. Maybe its the arch difference between x99 and z170 and something to do with PCI?

 

[tomkz]

Yes.... and No. There seem to be some quirks.... I thought i had it right, but then managed to bring the problem back by changing how they were plugged in... and I don't think IGFX had anything to do with it.

From what I can gather, and this is half guessing, OSX seems to remember what was plugged in where... and really doesn't like them being changed... and the monitors seem to need to be introduced carefully. Again - this might be complete BS that just happened to work, but having gone through it twice now, there might be something behind it.

The trick is getting one monitor to get detected on it's own. Once it is, and you are able to login, add a second monitor while logged in. It should get detected. Add that point, reboot. Add next monitor and reboot again. When I do it this way, and then don't change the cables, it seems to be working nicely even after reboots. If you want to change monitor cables / ports, it seems that you need to do it in the presence of OSX to keep OSX from freaking out after.

After I got the first one detected, I tried adding the other two right away... and that didn't seem to work... also had the system freeze on me a few times as I was adding the monitors... had some working with others not.... some stuck on the boot screen while others made it through... but at the moment, they're stable again.

Can't speak on the x99 difference.... but i do have them working, and i didn't do anything special with new patches.