I was able to successfully install Mavericks on my HP Z400 with the following steps
OS X 10.9.5 / UniBeast 4.0.2 / HP Z400
- Check Legacy USB Support when creating install disk
- Install LegacyAppleAHCIPortIntelICHx.kext onto USB disk (or LegacyAppleAHCIPort.kext, unsure of which)
- Boot: -x PCIRootUID=1 npci=0x2000
- Install OS X and reboot
- Manually install the kext onto the newly installed system disk and reboot
- Boot: -x PCIRootUID=1 npci=0x2000 -f
- Delete AppleHPET.kext
- MultiBeast Install, and include USB 3.0 - Universal
- Reboot
But I was unable to get audio working. Any ideas of which Audio Kext works?