Wow. I built my system in December with the below:
NCASE M1 V4
Asrock X99E-ITX
Intel Xeon E5-2676v3 2.4ghz (12 cores...this is an ES chip)
32GB DDR4-2133
MSI GTX 980 Ti 6GB
Sandisk Ultra 960GB SSD (Windows 10)
PNY CS1131 480GB SSD (OS X attempt)
I was fully unsuccessful with seemingly all other advice and guides on the internet until I hit this one, the first one to skip unibeast and all the pre-rolled solutions. I'm now up and running with 10.11.4 and the nvidia web driver!
I had lots of issues with the could not allocate memory error relating to the OsxAptioFixDrv-64.efi file. Tried everything including the OsxAptioFix2Drv-64.efi but nothing worked until I found the below file in the comments of an article somewhere. It seems to be a merged combo of the lowmemfix file and the AprioFixDrv file that seems to clear the memory allocation and allow it to boot just fine. If you're having issues relating to these files upon boot of installer or OS X itself, try replacing them altogether with this one, leaving the filename as is.
Only things I cannot get working are the included wifi+BT mini PCIE card (Azurewave BCM94352HMB) and almost more importantly any sound output. I installed the ALC1150 kext via multibeast but it did not seem to do anything even after a few boots now - nothing shows up in output or input. I have confirmed that my particular mobo does have ALC1150, is there anything else I can do here?
Thanks, your guide is insanely helpful!
:EDIT: Another thing I've noticed that breaks my system is seemingly every time I shut down and turn the system back on, it won't post and will give 5 beeps and shut back down. On the next boot, CSM (compatibility support module) is back enabled, I can tell because it changes the way the BIOS is displayed on my 4K display, and I have to go in and switch it back off to get my OS X install to boot again. Very strange, possibly related to my ES CPU?