What does a dual-boot Mac see?

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I'd like to set up my iMac to dual-boot, with on option being Mojave. I'd like to only use that Mojave to boot up when I need to run a 32-bit application. I want to have everything on a Catalina partition, possibly including the 32-bit application, but especially the 32-bit application's data.





When I boot to the Mojave partition, can I access data and programs on the Catalina partition?
 

Cory Cooper

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Hello again.

I think we have partially covered this previously, no? ;)

-Catalina will not run any 32-bit apps, so no need to store their data there.
-Catalina changes the entire disk format - It uses partitions/containers/vulumes. It creates an OS volume that is protected, and moves user data to another volume within the container.
-If you have two versions of macOS on a partitioned disk, you cannot run the apps on the other partitions. They will either not be compatible with the different OS versions, and their support files normally need to reside on the startup disk.

-You are currently running Mojave, correct?
-Is their a specific need you have to upgrade to Catalina right away?
-What app(s) are you worried about losing? (I can't remember)

C
 
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I'm currently trying to run a 32-bit app that I need on a VM-Fusion drive, but it is likely that I will get a new iMac for Christmas with more disk space. I expect I can dual-boot to the New Mac whenever I need that application if I do that, but I'd *really* like to have my data files on the Catalina disk. If I can't resolve my VM problem, I may have to do this (or wait until the middle of 2020 for my program to be updated to 64-bit).

So I think you're saying that if I use dual boot, my Mojave boot drive won't be able to see any data on my Catalina drive.

Right now my 32-bit application (kJams) runs, except I need it to see external monitors/TVs. I haven't resolved that issue. If I a TV into my Thunderbolt port and boot, my VM starts up on that TV. If I start my VM and then plug it in, my *real* mac can see the TV, but not my VM. I need my Mojave screen to be on my iMac which also sees the TV. (I'm hoping VM-Fusion can resolve this need)
 

Cory Cooper

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OK

The Mojave partition can "see" the data on the Catalina partition, but it cannot run apps from it. And, the support files for an app need to reside on the startup drive.

I see that kJams is only a 32-bit app, and they state on their website that they should update it in the future for use under Catalina. Their website also states the bit about running it in Mojave in a VMware virtual machine. That would work if you upgraded to Catalina. However, if you use kJams in a professional manner, I would wait to upgrade to Catalina until they support it. It wouldn't be worth it to go the Mojave/VMware route temporarily, due to cost and possible issues. However, you could simply clone your existing Mojave install to an external, which would bring all the kJams files with it. You could then do a dual-boot that way - startup from the external with Mojave on it when you need to run kJams, and startup from the internal running Catalina the rest of the time.

Am I understanding your situation correctly?

C
 
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I just run Karaoke twice a month in the senior living where I live. I also run kJams in my apartment for my own amusement and practice. In my apartment, I don't need separate monitors. Right now, kJams works for me in my apartment, with the data files on my *real* drive, and the executable on my virtual drive. It doesn't yet work for me when I take my iMac downstairs, as the VM doesn't see the separate monitors.

Your reply seems to be telling me that if I had dual boot, I could run it the same way. kJams allows me to have 2 copies. I used to have the backup copy on my wife's computer, but now I have one on my VM and one on my real computer. I could set it up to have one in the VM, and one on the Mojave partition, with the data on my Catalina partition.

This helps me decide what to do with my hardware. Right now I have a late 2013 iMac with a 1TB fusion drive with less than 200GB free disk space. My wife is talking about getting me an upgrade for Christmas. I'd sort of like taking a rain-check until the next iMacs come out (which I expect will likely be nice upgrades). But getting a new iMac for Christmas with a 2TB fusion drive and dual booting may be the better solution than waiting until mid 2020 for the kJams and iMac upgrades. At least it is a workable solution, and it may be a solution my wife likes better.

Now, if I could find an adapter to enable me to plug a Thunderbolt-3 disk drive into my Thunderbolt-1 Mac, I could buy a Thunderbolt-3 disk drive and dual-boot into it. But I don't want to buy a Thunderbolt-1 disk, and I can't find such an adapter.
 
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That looks like what I have, which I can use to plug Thunderbolt 1 devices into my wife's newer iMac.

The description is way too ambiguous and confusing. Which side is the "from" and which side is the "to"?

From visiting the Apple Store and Best Buy, they think I can go that way, but not from an older computer to newer device.
 

Cory Cooper

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"As a bidirectional adapter, it can also connect new Thunderbolt 3 devices to a Mac with a Thunderbolt or Thunderbolt 2 port and macOS Sierra or later."

C
 
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Looking at the various images, it looks exactly like the one I have, with a Thunderbolt 3 male plug and a Thunderbolt 1 female plug. If so, I can plug it into my wife's iMac, but not into my iMac. I guess "bidirectional" refers to how data flow.
 

Cory Cooper

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For clarification...

It is bidirectional for data transfer, as it can send read/write signals. It is also bidirectional as an adapter. The USB-C (Thunderbolt 3) end can be used on a device (HD) or a Mac port. The Thunderbolt 2 (backwards-compatible with Thunderbolt 1) end can be used on a device or a Mac port.

Since it has a female TB 2, you can use a TB cable between it and your iMac.

C
 
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I physically can't plug it into my iMac's Thunderbolt 1 female socket. The connectors are shaped differently. Thunderbolt 1 used a mini Display Port, Thunderbolt 3 uses a smaller USB-C port. The adaptor I want has a male mini-display port, and a female USB-C port, so that it can plug into my iMac's female Thunderbolt 1 socket, and allow me to plug in a Thunderbolt-3 disk drive into the other side.
 

Cory Cooper

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OK, I think I understand. Sounds like your drive does not have a removable cable...I thought part of the USB-C standard was removable cables? What brand model is the external USB-C (Thunderbolt 3) drive you have?

I don't remember ever seeing a female USB-C to male Thunderbolt cable or adapter.

C
 
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A friend offered to sell me his drive, but I don't know the brand. I just assumed it only had a USB-C (Thunderbolt 3) cable, as he used it for a backup on his Mac until he needed a bigger drive.
 

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