Bootcamp Install Issues on External SSD [MacBook Air 2020 + Mantiz Venus + RX 58...
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Bootcamp Install Issues on External SSD [MacBook Air 2020 + Mantiz Venus + RX 580]  


Active Member
Joined: 2 years ago

Hi Folks,

Despite all the help from all the great guides and posts here, I’ve been getting that feeling that I’m not getting anywhere fast over the past week, and thought I’d see if anyone can spare some insights. Smile

I previously had a working setup going with my 2018 MBA, Mantiz Venus, and an RX 580—with a small 50–60GB Bootcamp partition on the internal 256GB drive, and my Steam library on an SSD mounted inside the Mantiz. I’d have kept going with this, but drive space was becoming a real issue. I was running out of space on the Mac side, and didn't seem to have enough space to utilize restore points on the Windows side, which made managing the frequent rollbacks required to avoid Error 12 even less pleasant than they ought to be.

I thought I’d try and get Bootcamp up and running on the external SSD mounted inside the Mantiz, since I’ve no need for Bootcamp other than gaming while plugged into the eGPU.

This has certainly proved to be every bit as challenging as advertised elsewhere. 😉

Desired Goal:

MacBook Air 2018 [macOS 10.15.4 only] 
Mantiz Venus: RX 580 + 1TB SSD [Ideally partitioned three ways: Bootable Windows 10 partition, a Steam library partition for games, and a Mac-readable partition for extended storage]. Connected to monitor over DisplayPort.

What I've Tried So Far:

  1. I followed this guide, with these supplemental updates, to install Windows 1903 V1 on the formatted SSD inside the Mantiz via VirtualBox. I initially tried installing to a partition on that disk, but when I ultimately failed to be able to boot from that I thought maybe the partitioning was an issue and wiped the whole drive.
  2. The first part of the install (up until Windows restarts) within VirtualBox appeared to succeed on a couple of occasions. I let the VM restart once to continue the second part of the installation within Windows, as one commenter with a MBA2018 advised, but it eventually crashed before proceeding too far, and I was unable to subsequently boot from that drive. Most recently, as advised by the main guide itself, I shut down the VM before Windows restarted to complete the install.
  3. Subsequent attempts to boot into the Windows drive and finish installation fail. I get the flickering Windows logo a lot, which I presume is due to having the Windows SSD housed in the Mantiz, so in this configuration I have no way of hot-plugging the eGPU after Windows boot (which is what I always needed to do with my previous, functional, Bootcamp install on my internal drive), since both are in the same TB3 enclosure. Is this the Achille’s heel of this attempted setup?
  4. Following on from that assumption, and what I’ve read here, I am understanding I need to keep the iGPU enabled through the boot, while connected to the eGPU and SSD over the single TB3 connection.
  5. I have tried various combinations of rEFInd and the EFI hacks from these forums. Internal drive, USB stick, external drive. Currently referencing bits of sdedalus1’s thread and itsage's comments here  and have the following setup:
    1. I have rEFIND installed on the EFI partition of my internal drive
    2. I have copied 0xbb’s to EFI/custom/apple_set_os.efi
    3. I have added aa15032261’s revision to EFI/Boot/ (bootx64.efi renamed to bootx64_original.efi and the new bootx64.efi copied in)
    4. Here’s the internal drive’s EFI structure:
      Screen Shot 2020 04 29 at 11.31.25 PM
      Screen Shot 2020 04 29 at 11.31.46 PM
      Screen Shot 2020 04 29 at 11.31.59 PM


  6. Booting into rEFIND I see
    IMG 4220


  7. I select the leftmost option, boot EFI/custom/apple_set_os.efi from EFI, and I get the following error
    IMG 4222
  8. I then select the rightmost option, boot Windows (Legacy), and get this error
    IMG 4223
  9. If I try the Microsoft EFI boot option, instead, I do get as far as a flickering Windows logo
  10. Attempting to boot to MacOS from rEFIND gives me a white screen and does not boot. To boot into MacOS I have to alt-boot and bypass rEFIND completely.


I should note that I seem to get consistent results from these steps; sometimes attempting to boot into Windows gets me to a system repair screen or similar, but it seems I must have completely borked something in this setup, so rather than trying to dig myself in further I'm hoping someone might be able to set me on a better path*. Smile

Many thanks in advance for any and all help.


*I realize “better path” might well be an internal Bootcamp partition on a machine with an appropriately sized internal drive, but unfortunately that’s not an option at the moment 

MacBook Air (2018, 8GB) + Mantiz Venus + Radeon RX 580
macOS Catalina 10.15.4, Windows 10 Bootcamp

2011 15" MacBook Pro (HD6770M) [2nd,4C,Q] + RX 580 @ 10Gbps-TB1>TB3 (Mantiz Venus) + macOS 10.13.6 // Benchmarks [build link]  

Trusted Member
Joined: 4 years ago

@errantpixel, seems like there are at least 3 separate issues:

1. I believe you will need to boot Windows from a drive that is not in the Mantiz Venus.

2. It sounds like your attempt to install Windows to disk via virtual machine has failed. That seems like a very convoluted guide to install via VM. Is your internal Bootcamp install still working? Best to use it, or another Windows computer, to create an external boot disk. Create a small, temporary Bootcamp install on the internal drive first if needed. Be sure you have a successful Windows install that you can boot into and out of before trying to install egpu.

3. Your install of apple_set_os is broken. In the method in my thread, apple_set_os boots first, which then loads rEFInd (all via external thumb drive, from which I then boot into another Windows disk). In @itsage 's Mac Mini guide, he does not use rEFInd but installs apple_set_os to the internal drive; in his 2018 MBA guide, he uses automate-egpu efi manager installed to another partition on his internal drive. The error you see is fixed by aa15032261's modification to apple_set_os. I assume your hodgepodge of multiple methods (rEFInd + apple_set_os on internal) is messing something up. Specifically, I see you have both refind_x64.efi and bootx64.efi; in my instructions for the thumb drive, I replaced the former with the latter and use a different folder structure. I recommend you pick a successful method and follow the instructions closely. Good luck.


2018 Mac Mini [8th,4C,B] + RX 580 @ 16Gbps-TB2 (AKiTiO Thunder2) + macOS 10.14.6 & Win10 1903 // Win10 on external SSD [build link]

2014 13" MacBook Pro [4th,2C,U] + RX 580 @ 16Gbps-TB2 (AKiTiO Thunder2) + macOS 10.13.6 & Win10 1903 [build link]  

Reputable Member
Joined: 2 years ago

@errantpixel, use this guide I have made several copies and all work fine. I use the 1903 .295 version see my previous posts and other fellow member guides. 


A) 2020 MacBook Pro, i7-1068NG7, 32GB RAM, 1TB, EGPU Razer Core X, Nitro+ RX5700 xt 8Gb, Samsung 49 1440p UltraWide C49RG
Mac OS Catalina 10.15.7, Internal Bootcamp Windows 10 2004 pci.sys swap.
B) 2.7 GHz I7 4 Cores, 16Gb, 1TB MBP 13 2018 TB3 , EGPU Razer Core X, Nitro+ RX5700 xt 8Gb, LG 32UK550
Mac OS Catalina 10.15.2, Ext SSD Windows 10 1903 V1 .295

C) 2.7 GHz I7 4 Cores, 16Gb, 1TB MBP 13 2018 TB3 , EGPU Gigabyte Gaming Box RX580 8Gb, Mac OS Catalina 10.15.2, Ext SSD Windows 10 1803

D) 3.1 GHz I7, 16Gb, 1TB MBP 13 2015 TB2 , EGPU Gigabyte Gaming Box RX580 8Gb

Active Member
Joined: 2 years ago

Thanks folks. I confess that in the end I put my external Windows install dreams to bed, again, for now.

I’d been hauling around a 70GB iTunes/Music library for years and years on several different machines, but I finally faced up to the fact that I just stream everything all the time, and it’s been years since I really made use of local files. That gave me the courage to offload the music onto the SSD in the Mantiz—it’s not gone, I can get at it any time I really want, and most of it is already synced to Apple servers with iTunes Match so I can stream anything from my collection that isn’t on Spotify.

Long story short I freed up enough space to just go back to an adequately-sized Bootcamp partition. Maybe I’ll have another kick at the external install in the future, but even my partner was starting to ask some questions about what exactly it was that I was spending so much time trying to accomplish.  😉

MacBook Air (2018, 8GB) + Mantiz Venus + Radeon RX 580
macOS Catalina 10.15.4, Windows 10 Bootcamp

2011 15" MacBook Pro (HD6770M) [2nd,4C,Q] + RX 580 @ 10Gbps-TB1>TB3 (Mantiz Venus) + macOS 10.13.6 // Benchmarks [build link]