Bootable external drive for different OS's

I just found out this week that Intuit seems to be upping the OS requirement EACH year. After four years of doing TurboTax on Sierra, I had to upgrade to High Sierra last year, and it gave me a warning that I’d need to be on Mojave this year. I got around it last year by upgrading an older external drive as a boot drive. It was fine once it was up and running but booting was miserable. (it was the original drive from my 2008 unibody, so no surprise there)

I also just acquired a new Quickbooks client who was on the 2020 version, which requires Mojave. The 2021 version requires Catalina.

I still have some big ticket items that are 32 bit. While I have another machine I could offload them to, I’m a bit reluctant to make my main machine a guinea pig for the latest and greatest, when I know what I have works fine (for me). Without Intuit issues, I think I am comfortable bringing the laptop to Mojave.

Long story short, I’m looking for a smaller external drive that will boot in a reasonable amount of time, for these programs that need a higher OS that I won’t use daily. Not big and not expensive (in a perfect world).

For those that remember my post on a new internal drive, yes I have it, no I have not installed it yet and most importantly, I usually do a fresh install with a new drive and keep the old one for awhile as I bring software and files over. I’ll be needing to work on client files before I’m ready with that one.

It’s been awhile since I’ve worked with multiple systems on the same drive. Am I correct that each OS needs its own partition?

Is there any other option I should be considering? i.e. my new internal 480gb drive… would it be possible to create tiny partitions on that for this endeavor? Gee maybe I should swap it for the 1T after all :confused: I’d hate to use my extra space on something like this


Thanks - again!
early 2015 MBPr currently with 256gb, going to 480gb soon

If it’s just about a couple old apps, I’d say you should be able to get by with a small SSD in an USB case that you can interface over 5 Gbps USB3. It’s not hyper fast, but it should be just fine for light work every once in a while.

Personally, I’m not a big fan of partitioning. I like to keep my various OS versions separate. Too many delicate eggs in one basket IMHO. And an external drive means I only have to deal with it when it’s hooked up and I’m actually using it. Once I’m done it goes into a drawer and it’s out of my way and sight.

For a similar purpose I just got one of these the other day. $28 for 240 GB. Plenty for macOS and a couple old apps and docs.

For you, this case would work just fine out of the box (USB-A), $9.

Simon - you’re great! Thank you! Have you got it working yet?

It’s actually NEW apps that will be going the external but only a couple. I can’t see upgrading my entire machine for TurbotTax OR Quickbooks, when I don’t use them daily (or even weekly).

Going to check those out now……


Oh yeah, sure. These things are a cinch to get set up. The cases require no tools. You just drop the SSD in and connect the case to your Mac. Format with Disk Utility. Done. :slight_smile:

Happy with the boot speed? Though I’m guessing anything is better than the OEM drive from a 2008 unibody, in an external case from around 2013! :laughing:

I can probably get by with a 120gb setups for Catalina…… but wait - do these OS upgrades do any firmware updates too? I read that I need to upgrade to High Sierra before starting my internal drive upgrade for that very reason. Last thing I need is to make a bootable external for a newer OS and mess up my machine?!


The biggest caveat to running a new system as a secondary system on an older machine is that as soon as you install the new system, it will update the firmware of the mac. Firmware is only tested to be compatible with whatever system versions were still supported by Apple at the time of the firmware release. So for High Sierra, you’re probably ok with installing Catalina, but Big Sur could cause instability with systems older than High Sierra. There’s no way to revert to older firmware. If you have a less sensitive mac available, you could install the system form that one, then run it on your main mac without forcing a firmware update.

Howard Oakley has written a lot about firmware issues. including the recent and excellent “Firmware Fundamentals” (even skimming the summary at the top should be enough to get a good grasp of things):

Firmware fundamentals – The Eclectic Light Company

Have you considered installing a current system as a virtual machine? That won’t touch the firmware on your mac. VMs are a lot less hassle than dual booting–it lets you be running both at the same time, including copy/paste and file dragging between them. VMWare Fusion is now free for non commercial use and has jacked the price to $150 otherwise, but it’s a perpetual license. Parallels has an $80 license (home & student), but you’d need to check to see if that covers any commercial use. Otherwise it’s $100/year. The other option is the open source VirtualBox, but it’s harder to work with and lacks many nice features from the commercial ones. You can keep the virtual machine on an external SSD if your internal is short of space, and it should be fast enough. If you only have 8GB ram it will slow things down, but it should still be fine for occasional use.

I wasn’t sure about firmware, I mentioned it on one of the posts. :-/

To upgrade the SSD in the 2015 MPBr, I already read I have to update to High Sierra first. I think I’m ok with going to Mojave on this machine but I don’t want to go further as I’ll lose too many apps.

I think you’re saying that installing a later OS on the external drive will update the firmware of the Mac, but not if it’s in a virtual machine?

I would definitely consider a VM. I downloaded a Parallels client for a project earlier this year, which I was surprised I didn’t have to pay for, but maybe because I was using it to attach to an existing system. I may have bought it at some point in the past so I need to look through my emails for a license.

I have VirtualBox installed on another machine, to access Eudora an and old version of QB. It was miserable to setup and when I can ever catch my breath, I’ll be pulling those back down to my 2008 unibody.

I have 16gb of RAM in this machine.


Here’s a crazy question - what would have been a free (or really cheap) Windows emulator around 2007? I used to run a Windows app on my iBook in that timeframe and can’t remember how I did it.


5 minutes later…. found it randomly… it was VirtualPC (Microsoft). I think I even had the original version. No longer an option I guess!


I think you’re saying that installing a later OS on the external drive
will update the firmware of the Mac, but not if it’s in a virtual

Yes. Apple is picky about what can alter the firmware for good reasons, and doesn’t let anyone else do it legitimately. It happens with OS installs and some kinds of system updates, including some security updates. Virtual machines emulate the functions of firmware that they need such as letting you boot a VM to recovery mode.

16 GB will easily let you run a VM without a fuss.

Mojave might be a better choice than High Sierra all other things being equal. HS was one of the ‘lots of new stuff’ versions including the new APFS file system, and Mojave changed some things about that. But you can always do one or more each. There’s no limit to how many VMs you can have other than the disk space they use. You probably wouldn’t want to run more than one or two at the same time though. I’ve accumulated piles of them–some to run one particular app that’s too intrusive to install on a primary machine, some for trying out random software, some for old stuff, some for work stuff… They currently range in size from about 25 GB to 150 GB.

It occurs to me that you’ll need to check the system requirements for both the host mac and the virtual mac. I’ve lost track of which system you’re running now–if it’s still Sierra, you’d need to get an older VMWare version, 11.1. (11.5 needs HS, the current 12 needs Catalina) That would let you run clients through Catalina. For Parallels, you need version 15 to run on Sierra (current 16 will run on HS+), and it will run though Catalina. I don’t know how easy it will be to find older versions. It’s worth asking customer support, and if that fails, maybe amazon or ebay.

Host system support by Fusion version:

VMware Knowledge Base


Fusion supports the following Mac server and client versions for the guest operating system:
Mac OS X Server 10.5, 10.6
Mac OS X 10.7
OS X 10.8, 10.9, 10.10, 10.11
macOS 10.12, 10.13, 10.14, 10.15

Fusion does not support the following features for Mac OS X virtual machines:
Multiple displays
3D Accelerated graphics
Unity view

Parallels requirements for hosts and clients:

It’s an early 2015 MBPr 13”, 256gb (soon to be 480gb), 16gb ram with Sierra.

I have to upgrade to HS anyway, just to do the internal hard drive replacement. I was on the fence about going to Mojave internally. I have one app I may lose in HS but I can move it to a different machine. Actually, it still works when I boot off an external HS drive, but I’m pretty sure I’ll lose it in Mojave.

So at the moment it’s looking like HS for the internal drive initially. And…. now that I re-read your comment, I probably have already updated the firmware from using this machine to update the external to HS a few months back. I will be reading that link you sent, later today. Anyway….

QB 2020 and TurboTax this year are going to require Mojave. I’m thinking I can format the external with High Sierra and create a Mohave VM for now so that I can get up and running with this client. If I have a free block of time when I get the external, I may just try VirtualBox again. They say the new version is a bit easier to setup than the older ones and I was working with such an old OS that I wasn’t doing myself any favors. If that proves too frustrating I will suck it up and buy Parallels or Fusion. I didn’t see any current sales on stand alone systems, just subscription for Parallels, which I hate with a passion. I’ll confirm everything with customer support before buying.

You know, I actually miss this part about playing with systems. I wish everyone would go back to putting out products that wow us on a less frequent basis, because I feel like I don’t even get a chance to fully learn and enjoy what I’m using before something new comes out and breaks it.

I was rummaging through my backup drive last night, what a trip down memory lane with apps! In the past it seems I’d used at least once, Codetek Virtual Desktop and Crossover.

Thanks for the help :slight_smile:

VirtualPC is designed to emulate a PC hardware environment on a PowerPC Mac. It won’t work on an Intel Mac.

If you’ve got an Intel Mac and want to run Windows apps, you definitely want to use a virtual machine environment. Popular VM packages are: VMWare Fusion, Parallels Desktop and Oracle VirtualBox.

I have never tried to run Windows in any of these (I use VirtualBox, but all of my VMs run Linux), so I can’t recommend any of them. I do know that you will need a Windows license to legally run Windows in any of the three environments (I don’t know if any includes a license the way VirtualPC did).

At the moment I need to run a different Mac OS on my current Mac. I just knew I’d run Windows on an iBook in the past. I have snippets of various emulators scattered on my backups.

I setup VirtualBox a couple of years ago on an iMac and have read the newest version is a bit easier! I was setting up a Snow Leopard partition at the time because I got tired of dual-booting.


Don’t you have to get the next years version of TurboTax to do your taxes? You can’t use Turbo Tax 2019 to do your 2020 taxes, for example?

Yes, you need a new version of TurboTax every year. But Intuit never upped the system requirements every year. And you DON’T need Quickbooks every year, that’s a money grab.


Hi Simon - I got the drive and case! I made it bootable though I guess I didn’t need to. I downloaded a trial of Parallels and have set up 2 VMs, though I did them while booted to the external and I think I should have done it the other way around as I’m getting an error on the Mojave VM when I access it from a laptop boot.

Anyway, one thing I’ve noticed is that if I have booted to the external, then re-set the startup disk to the laptop and reboot, I then lose the external. If I unplug it and plug it back in it shows up like nothing happened.

If I am on the laptop and do a simple reboot it’s fine too. It just disappears when I change startup disk to the laptop.

Have you noticed anything like that?

Anyway, great little concept even though it’s not quite “no tools” like advertised! (at least for me lol)


What do you mean by ‘lose’? It’s not showing up in Finder? Or in the boot manager (opt held during boot)?

Unfortunately (or fortunately in this case) I have noticed that when booting from an external drive Firmware updates don’t seem to be applied by the system, the drive must be internally installed for the Firmware update to happen.

I.e.: You can boot from an external APFS drive in High Sierra from a Mac that has an old Firmware but not from the same drive installed internally (it won’t even boot unless you the Firmware is upgraded first). No Firmware update should happen when you boot from the drive when it’s in an external enclosure!

Just my experience, but even though I have the most recent Big Sur firmware on my iMac, I have not experienced any issues when occasionally running Sierra through Catalina. Not saying that might not change in the future or that someone with a different Mac model running and using different aspects of macOS or applications might be having issues.

It’s nowhere, as if it’s not plugged in. I thought I could boot off it indefinitely but that doesn’t work either.

I plug it in and get one boot (either using it as a startup disk or my laptop), then on the next boot it’s gone, no light even.

But I can leave it plugged in all day and it seems to be fine. Not a huge deal but I’ll reach out to the company and see what they think.

I think it’s a great little setup and will get a another soon.

This is faster than a USB stick would be, right?