So just want to share my latest experience and add my contribution
F8 BIOS completely sucks for me lol. Got the allocation error as soon as I set up my config after flashing. I had disabled the same items as before and enabled above 4G (of course they removed the ability to disable onboard NIC, so had to disable PCH NIC instead). Resetting CMOS didn't change a thing
I wasn't liking the new (advanced) interface either, so reflashed to F7, set things up as before, and I'm back in business! So there really is something to how each UEFI firmware handles things...
The interesting thing is that on F7, I can boot macOS using slide=0 and AptioMemoryFix, IGPU enabled (64MB DVMT),, CSM enabled, WIFI card removed, onboard NIC (I211) disabled, VT-D enabled, above 4g enabled... Regardless of booting from f12 menu, booting from disk, booting Windows from Clover or from disk directly, boots every time (knock on wood lol).
I'm using an RX 590 and a Texas Instruments PCIE firewire card installed as well... But none of this seems to affect whatever memory space is available for the kernel.
Have any of you guys on F7 tried enabling above 4G memory space? I know it has been said that we shouldn't use this setting, but then again, we were also advised not to use OSXAptioMemoryFix2DRV-free2000 lol... Has anyone on F8 BIOS been able to main successful boots using AptioMemoryFix?
That's all for now