install bootcamp on external disk
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install bootcamp on external disk  

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Active Member
Joined: 12 months ago

I think the easiest way to have windows install on external ssd is using wintousb. 

You can first install windows using bootcamp manager. Then after you in have a working copy of windows, download and install wintoUSB and use it to install windows on the external drive.I have don't it many times and it worked. 

You could also do manual installation using the dism via command prompt in windows. But that is a more involved process. And from my experience, I couldn't format the EFI partition to FAT32 for some reason in my bootcamp. So maybe you need a separate native windows machine to do that. This method also worked 100% of the time for me. 

Lastly, I didn't managed to get eGPU working when booting windows from an external SSD. I get the error code12. I didn't spend much time trying to solve it..

Im using a MBP 16". eGPU is Razer Core X Chroma. If anyone managed to connect eGPU when booting windows from external SSD, please teach me how to do it. Thanks

2019 16" MacBook Pro (RP5500M) [9th,8C,H] + RX 5700 XT @ 32Gbps-TB3 (Razer Core X Chroma) + macOS 10.15.5 & Win10 1903 [build link]  

AJ Scarcella
Trusted Member
Joined: 2 years ago

During the Windows install, there is a point where it’ll prompt that it’ll reboot in ten seconds. You have to simply shut down the virtual machine at that point by quitting the app - i.e. close the Virtual Box app, not cancel the install. 

Not sure where it’s going wrong - it worked fine for me. 

Mac Pro 2013
OWC Mercury Helios FX
Radeon RX 580 8GB

Leandro Glossman
Active Member
Joined: 1 year ago

The way I achieved this is by first installing bootcamp on my internal disk and have it set up the way I wanted. Then I installed Winclone on MacOS, created an image of my bootcamp partition and then transferred it to my external drive. Worth mentioning that winclone is a paid app but you can probably use one of their betas available here

You might need to adjust registry (BootDriveFlags = 0x14) a little bit as this post indicates, although I had to do it only once for the many times I followed this approach.

One problem that I couldn't overcome was the dreaded "Error Code 12" that only happens to me when booting from the external drive and not when from the internal one. I tried all this things but still couldn't solve it:

- Update to latest from Insiders Preview Dev Channel
- Use efi loader from here (produces different results but still doesn't work)
- All possible port combinations
- Disabling unused PCIe port 1909 and even 1901 where discrete gpu is connected (i was able to see the egpu led turning on but still no image)

Macbook Pro 2019 16" + Aorus Gaming Box upgraded with regular Gigabyte RTX 2070
Oculus Quest + Link

Trusted Member
Joined: 2 years ago

Just to add to this thread, the part about putting a bootable Windows 10 on an SSD has gone quite smoothly for me... like a half-dozen times at least by now (with different Windows variations, etc.). This video walkthrough is excellent:

Then comes the eGPU part, which I've had zero luck with after probably 40+ hours of trying. 🙁

I'm considering going back to using precious internal storage space again, as I'm wondering if eGPU + Win10 on external SSD is even possible. I previously had my eGPU + Windows 10 running fine under Bootcamp until a Windows update killed it (and I didn't have a restore point... but it was with v 1809).

Anyway, just wanted to pass along that getting Windows/Bootcamp going on an external drive is relatively straight forward via a VM and utility.

2018 Mac mini (i7, 16 GB RAM, 256 GB SSD) - Blackmagic eGPU (RX580)

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