Hi All, I just wondered if anyone can help me. Please bear with me as this seems very freaky to me. i have a Mac Pro 3.1 and patched with Dosdudes High Sierra patcher that was running great, that is until I read that maybe I could install Mojave with his patcher as well, no joy and then I emailed him about it and he said my GTX 5780 wouldn't work properly unless flashed and pointed me to his video on YouTube, I watched it several times and eventually decided to have a go. I needed to install BootCamp and Windows so set about doing that on a spare SSD, all went well after a few hiccups and I was able to install Windows 10 Pro, however there was no icon to right click on, on the taskbar to go back to High Sierra, so I rebooted and pressed the alt key on the chime as you should. No boot up at all, in fact all it showed was a black screen, no apple logo, no nothing, I rebooted again with out pressing the alt key and it booted to Windows, I took out the Windows HD and tried again, all I got was a cursor on a black screen, I did a SMC reset and tried a PRAM one which didn't happen, I even went inside and pressed the little buttons, one by the Graphics card and one under the memory case.
I tried several times with these resets to no avail, it only boots in Windows 10, I put a fresh HD in and tried to re-install HS via the flash drive patcher I still had, it wouldn't load at all just hung, so all in all I have now got a very fast Mac Pro Windows 10 computer, has anyone any thoughts on how I can get my beloved Mac Pro back up and running the OS it is designed for ? I can live with it being Windows only,if I have screwed it completely as regards having a an Apple OS in it, at least it isn't fully broken and heading for the smelter.
Well thanks for hanging in.
Keith
That's a very curious case, I suppose you have personal datas on the old High Sierra partition you don't want lose. Most probably something has altered the EFI Apple Boot structure.
Probably you have a corrupted EFI partition, it is fixable in most cases.
TRY THESE STEPS ONLY if your HIGH SIERRA was installed in HFSplus, cause these steps won't work with an APFS file system.
I'd suggest you to create a MacOS USB Installer (minimum El Capitan), then booting from it holding the option key, and launch "First Aid" from Disk Utility, after check if from there you can see any HFS partition apart the NTFS Windows one.
You could create an HFS EFI bootable USB even from Windows with the proper tools!
One advise: don't user Clover on real Mac, never.
If you don't have another Mac, you will need to do from Windows using the diskpart (that is the equivalent of diskutil in unix) to convert your 16 GB USB empty drive in GPT partition scheme (the only one any Mac adopts).
Wait, you could use "Rufus" windows software to format your USB drive in GPT, much simpler.
You could use even an older MacOS Installer DVD to gain access to an unix Terminal or Disk Utility to check what's going on your main HDD, maybe a couple of "First Aid" could even fix.
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Or since your Windows from Mac is working you could try:
a windows software "transmac", plug in an empty 16 GB USB drive, launch transmac, right click the USB Drive and select
Format Disk for Mac, then right click the USB Drive and select
Restore with Disk Image, select your (pre-downloaded) dmg (OSX El Capitan Installer) file and click Open. It will take some time to create the USB MacOS Installer, then holding option at boot you could be able to boot from it trying the DiskUtility's First Aid.