I've got my Hack working beautifully with the following setup:
ASRock X99 Extreme4
Clover 2.3 r3333
NVidia web driver 346.03.05f01
It works *really* well. Got audio (both HDMI/DP and ALC1150), got power states, got turbo, got USB, probably have other things working I've forgotten about. But no sleep/wake.
To be specific, sleep appears to work. It takes maybe 20 seconds but the real Mac right next to it takes almost as long. Power consumption drops to ~3W at that point.
Wake is where it all goes wrong. System will wake via keyboard or mouse click (and I think by power button). However within a second, I hear a "click" that's generally associated with a full reset, and the system proceeds to reboot. All of this happens in the dark -- nothing bothers to turn on the display until the OS has finished loading.
A very few times (and maybe none since swapping monitors from DVI to DP - unrelated to this) I've gotten some visible output before the reboot. Sample attached here.
One more note; this same hardware handles sleep/wake flawlessly under Linux and Windows 10.
I've done tons of searching (and found a few similar issues but none on X99) and tried numerous Clover settings and some DSDT tweaks but without any luck. It does seem like a DSDT issue but to be honest, that's just a hunch.
Any suggestions of what to try next would be most appreciated. It's so close to "perfect" that I'm kind of obsessed with having sleep/wake working.
Oh, if anyone else is trying to make progress with an X99 Extreme4, I'm happy to share what's worked for me. There don't seem to be a lot of folks trying to run OSX on this board.