Boot Choices - Mojave or Mountain Lion

[Rich M]

I have a Mid 2010 Mac Pro that I use primarily for editing video. I bought this machine when Final Cut Pro 7 was the go-to video editing app on MACs. After several years of using FCP 7, I installed FCP X. I have become very comfortable with FCP X.

I have two bootable hard drives in this MAC. Prior to the Mojave upgrade and the Radeon RX 580 metal video card install, I could choose which OS to boot into by holding the Option key down during boot up. I need this dual boot capability so I can go back to older FCP 7 projects and use the SendtoX app to port them over to FCP X.

Since the Mojave upgrade and the Radeon RX 580 metal video card install, I can no longer dual boot via the Option key. Is there a way to do this with the hardware I now have?

 

[Slydude]

I'm assuming that you are using the built-in keyboard when you're doing this? Some wireless keyboards are a bit slow to react on boot up and may not work reliably that early in the boot process.

The following solution is a bit of a pain boot should work. When you need to switch the OS that you're booted into go to the Startup preference pane and select the OS you want to use. That should work for both OS versions.

 

[krs]

Since the Mojave upgrade and the Radeon RX 580 metal video card install, I can no longer dual boot via the Option key. Is there a way to do this with the hardware I now have?

I don't see how your Mojave upgrade or video card replacement could have anything to do with your problem. I use a 2012 Mini and have no trouble booting up in Mojave or El Capitan via the option key.

I assume you can boot up in Mojave but the other macOS (you didn't say which one...ooops - it's in the title) doesn't show when you hold down the option key.
Check disk utility to see if both hard drives show - if they don't then check the hard drive and cables in the Mac Pro. Maybe something got disconnected when you installed the video card or one drive is dead.

 

[chscag]

Since the Mojave upgrade and the Radeon RX 580 metal video card install, I can no longer dual boot via the Option key. Is there a way to do this with the hardware I now have?

I agree with member @krs in that Mojave should not make a difference for the boot process. I don't know enough about replacing the video card with a metal card (Radeon RX 580) to say whether that could be the problem.

We have several of our members who are more familiar with the Mac Pro who may be able to shed some light on what'a happening.

 

[Rich M]

Both boot drives are mounted. It is a single 480 GB SSD, partitioned into two drives. When I am running Mojave, I see them both.

I tried setting the start-up drive to the old OS (Mountain Lion). I think the computer booted, but I'm not sure. I heard the musical chord that plays when a MAC boots. However, NOTHING appeared on the monitors (dual monitors). They remained black. No desktop. The only way I can see anything in Mountain Lion is to remove the Sapphire RX580 video card and install the old ATI Radeon video card. Then the computer will boot into Mountain Lion normally and both monitors display properly.

However, now I have a huge new problem. When running Mountain Lion, if I go into System preferences and choose Start Up Drive, the Mojave boot drive does not appear! If I run the Disk Utility app, the Mojave drive shows as an unmounted partition named "diskOs2" and I cannot mount it.

I am posting this while running Mountain Lion. I don't see a way to boot back into Mojave! Now I am really dead in the water.

 

[krs]

It sounded from your first post as if you had two separate drives, not a single drive that was partitioned.

I think one potential problem may be that Mojave uses a different file system than Mountain Lion - not sure how that plays on a partitioned drive. In my case with Mojave and El Capitan, I have two different physical drives, one is a spinner and the other an SSD. The spinner uses HFS+, the SSD APFS.
So....for the last "problem" which isn't really a problem, the partition with Mojave on it won't show with Mountain Lion since ML can't recognize the new APFS file system.
On how to resolve this issue....hmmmm
I let someone else comment.

PS: Have you tried going back to the original video card and holding down the option button while booting?
I think that should bring up both macOSs if it did before.

 

[krs]

And the original problem seems to be an incompatibility between ML and the Sapphire RX580 video card.
Did you have to install any drivers for that card?
Or is there any info on which macOSs the card is compatible with?

 

[chscag]

I think one potential problem may be that Mojave uses a different file system than Mountain Lion - not sure how that plays on a partitioned drive. In my case with Mojave and El Capitan, I have two different physical drives, one is a spinner and the other an SSD. The spinner uses HFS+, the SSD APFS.

Good catch. Very definitely could be the root of the problem.

 

[MacInWin]

And I suspect that it's not that it didn't boot, but that the drivers for the video card aren't loaded so you can't see that the screen is telling you to do something, like log in. Maybe try, when booted with the old card, to set that ML partition to automatically log in.

 

[Rich M]

I was able to get booted back in Mojave using the Option key on boot up. Whew! Only one monitor with the old video card, but at least I can now get back to work after I change out the video card again.

I think the problem is what MacInWin said, that Mountain Lion does not know how to communicate with the Sapphire RX 580 video card. I will try to find drivers for it on the net. If any of you know where to find them, I would appreciate a link.

Thanks for you help here. I'll keep you posted on this.

 

[Rich M]

PROBLEM SOLVED!

MacInWin, you pointed me in the right direction when you said that Mountain Lion does not know how to communicate with the Sapphire RX 580 video card, and you were correct.

Here's what I did...

• I installed the old ATI Radeon video card so I could boot into the old OS - 10.8.5 Mountain Lion.
• I downloaded OS Sierra 10.12.6 from Apple.
  This is the last version that allows the old Final Cut 7 to run.
• I upgraded the OS from Mountain Lion to Sierra.
• I shut down the machine without making any change to the start up disc.
  I wanted the machine to boot back up into Sierra.
• I removed the old ATI Radeon video card.
• I installed the Sapphire RX 580 video card.
• I restarted the machine.
• IT WORKED! The dual monitors properly displayed the desktop.
• I started FCP 7 and it ran fine.
• I changed my start up disc to Mojave and rebooted.
• All OK in Mojave and FCP X.

When running Sierra I had to install an updated driver for the AJA Kona LHi capture card and reset some of my preferences in FCP 7, but that's it. FCP 7 works fine in Sierra, and nothing has changed in my Mojave setup where I now work every day in FCP X.

My thanks to all of you who posted in this thread. This has been a major headache for several months. I'm glad we got it solved.

 

[MacInWin]

Glad you got it sorted out.

 

[Slydude]

Thanks for the update. Nice bit of troubleshooting there.