Boot Mac Pro into macOS from Windows

barry.pearson

macrumors member
Original poster
Jan 26, 2016
42
2
England
This is now solved. It was fixed by doing the PRAM reset but waiting for four chimes rather than the usual two. Thanks to Skizzo for the answer.

Hey, just at my wit's end here. I have a Mac Pro 4,1 (firmware 5,1) and I have Windows installed. After a recent update I had an issue and reinstalled Windows 10 with the built in startup recovery. Now my Apple software is gone and I'm unable to restart into macOS.

I have loading into the startup disk selection by holding Alt/Option upon boot. Although I'm using a RX570 with no boot screen support, the Mac just boots into Windows 10 regardless. I've tried removing the Windows 10 drive and booting with only my macOS drive installed and the Mac just boots to a black screen with a blinking cursor.

I would be very thankful if someone knows another way I've not tried to get back to macOS from Windows.

Thanks in advance!
 
Last edited:

casperes1996

macrumors 601
Jan 26, 2014
4,107
1,999
Horsens, Denmark
I have loading into the startup disk selection by holding Alt/Option upon boot. Although I'm using a RX570 with no boot screen support, the Mac just boots into Windows 10 regardless. I've tried removing the Windows 10 drive and booting with only my macOS drive installed and the Mac just boots to a black screen with a blinking cursor.

Do this again, but also reset SMC and PRAM. Might reset the boot flags for where to boot from.

Alternatively try searching to see if you can find the bootcamp tools for Windows for download
 

barry.pearson

macrumors member
Original poster
Jan 26, 2016
42
2
England
Hi, I've already reset the PRAM with no luck, and I've downloaded the various Windows Bootcamp files (one from my iMac through Bootcamp and one from the Apple website) and neither work. I just get a message saying that those files were not designed for my computer.

Looking at resetting the SMC, I had also done that (inadvertently while swapping drives around). I've tried it again and still boots into Windows 10 upon boot.
 

barry.pearson

macrumors member
Original poster
Jan 26, 2016
42
2
England
Could a Windows 10 update do that? Is there a way to restore it without access to macOS on that machine?
 

skizzo

macrumors regular
Apr 11, 2018
238
68
how many "chimes" did you do when resetting PRAM? I would do at least 4 in a row to make sure it "took"

and do that with just a single macOS SATA disk installed. remove all other macOS and Windows disks until you get the issue resolved

you don't get boot screen support with the RX570 so any attempts of using the ALT key to see the boot picker is useless

you have other apple systems it looks like too. so make sure the macOS disk you are trying to boot from on the cMP still boots from another system....just another thing to double check and cross off the list of variables
 

skizzo

macrumors regular
Apr 11, 2018
238
68
I have done the same thing, only did one or two chimes and nothing was "cleared" it seemed since even some kext hacks were still loading up. After that event I always do 4 or 5 chimes. Every time I have tried less it seems like it did not clear what it needs to. glad it worked!
 

h9826790

macrumors G5
Apr 3, 2014
12,985
5,863
Hong Kong
1) shutdown

2) remove all hard drive EXCEPT the macOS hard drive

3) use a wired keyboard to perform PRAM reset (4 cycles)

you should now back to macOS

update: it seems you got it already.