Just wondering, did you install 10.8.4 through a USB installer?
No I actually installed 10.8.4 to a thumb drive, then ran the Haswell Helper app on the installation (to install the patched kernel), installed Chameleon and the usual kexts. All this done from a regular Mac. Then I used that full installation on the thumb drive to boot my mobo from without any issue.
All went very easily that way. I did try to install from a USB installer, but for some reason that failed, but as I have used my method before I did not persist with the USB installer stick method and went straight for installing onto the USB.
I then cloned from the USB drive to internal disk and ran chameleon on the internal drive to get it bootable.
I tried the same method for 10.8.5 and for Mav, but unfortunately stuck on the reboot loop. To save hassle for experimenting though I have got the Mav install now on the second internal partition so I can keep trying.
It is very baffling at the moment. I guess an answer will come sooner or later, but I really hope it is sooner. It looks more serious to me than an ordinary KP.
Well not all Z87s are borne the same! I am having great success with GigaByte Z77M-D3H where as my MSI Z87M-G43 would not boot any version of OS X that I tried (and I tried them all; and the board did install and run MS 8 and Ubuntu 13.4). I am able to run 10.8.4 with the patched kernel and/or the kernel from the MBA Haswell release; all version of 10.8.5 and all versions of DP 10.9 with the Gigabyte MB.
And now with Chimera 2.2, I am able to run HD-4600 with full acelleration on 10.8.5 current version but without a GPU card installed. Still need a guide for running internal Intel graphics and an GPU card concurrently.
What does this say? Well only that there is a lot of sorting out to be done.
Hmmm, well maybe I should (just this once!) have taken a safer route by going with a Gigabyte Z87.....having said that I have (as you know Neil!) had good success in the past with Zotac boards.
I didn't use my usual routine of updating to the latest bios before I started though, so I may just go back and do that in case Zotac have already solved the problem for me (in which case I'll have to wipe a bit of egg off my face!).