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Run Windows 10 from an external SSD disk? Yes, it works!

This is what I have done to make it work. The whole process takes approximately, 45 minutes but I think it is really worth it if you want to run a fast and clean installation of Windows 10 on your iMac.


What you need:

  • An external SSD disk - Data will be erased ⚠
  • An iMac 27" (Late 2013 in my case)

Temporarily, for the installation, you will also need:

  • A running computer with Windows 7, 8 or 10 to copy the right files onto the SSD disk and make it bootable
  • A running computer with OS X to download the BootCamp software
  • A USB thumb drive - Data will be erased ⚠

First, in Windows, get yourself an ISO file of Windows 10. You can use the Media Creation Tool provided at https://www.microsoft.com/en-gb/software-download/windows10 and choose to save it as an ISO file (do not create a bootable USB media).


  1. Double click on the .ISO file. This will mount the installation disk onto a drive (in my case, letter E).
  2. Plug the SSD drive onto a spare USB port
  3. Open a Administrator command prompt and type:
    1. diskpart
    2. list disk (identify the number of your external SSD drive)
    3. select disk 2 (or another number for your external SSD disk, be careful not to wipe your internal disk, usually on 0).
    4. clean - Be careful, if you have selected the wrong disk, it will erase all the data on it
    5. create part pri
    6. format quick
    7. assign letter=Y (or another letter if already used)
    8. active
    9. exit
    10. dism /apply-image /imagefile:"E:\sources\install.esd" /index:1 /ApplyDir:Y:\(change E to another letter for the mounted ISO file)
    11. BCDBOOT.EXE Y:\WINDOWS /S Y: /F BIOS (this will make the drive bootable in BIOS only (not EFI)
    12. exit
    13. Eject all drives cleanly or simply shut down your PC.


Secondly, on your Mac, open BootCamp assistant (click on Launchpad and type "bootcamp" to find it) and ONLY tick "Download the latest Windows support software from Apple". Save it all on your USB thumb drive. Shut down your iMac. Remove the USB thumb drive and keep it in your hand.


Power up your iMac by pressing the option key (alt). You will see an orange icon with Windows. Select this and wait until you see "Getting devices ready", wait a little bit longer until you hear the startup chime and press the option key (alt) again to make sure you boot on the external drive. That's it!


Now you have a copy of Windows running from your external USB drive. You just need to install the BootCamp drivers on your USB thumb drive (\Bootcamp\Setup.exe). Reboot.

That's it, you've got Windows 10 running natively on your beautiful iMac.

Enjoy!

iMac (27-inch, Late 2013), Windows 10, null

Posted on Jun 10, 2016 1:48 AM

Reply
38 replies

Jun 26, 2017 11:53 AM in response to LFGL

These instructions do not work for later model Macs. Later macs require GPT. Additionally, EFI is required. Do not add "/f BIOS" to the bcdboot command.


Configuring an externally bootable Windows drive will require a computer running Windows. Running Windows in a VM on a Mac will do.


Follow the instructions here for setting up a drive using GPT: https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/configure- uefigpt-based-hard-drive-partitions#span…


These instructions will copy Windows to the drive along with boot and recovery data: https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/capture-an d-apply-windows-system-and-recovery-part…


Note there is no need to create an image if you've already downloaded the Windows ISO. Mount the ISO and use <drive letter>\sources.install.esd" for the image to apply.


Once all is done, reboot your Mac while holding option. After Startup Manager appears, plug in the Windows drive. It should appear. If it doesn't then review your steps. Something is missing.


Good luck.

Oct 26, 2017 10:00 AM in response to Digitalclips

Hi,

So I'm trying to install windows 10 on an internal ssd with sata Adapter. I followed a lot of different methods and some worked that I can Boot windows. But as soon as I start using any programs it gets extremely slow and the loading times go into infinity. I tried your way with wintousb, I tried the first way opened by this post and I tried it with Rufus over windows but every time I encounter this error. I'm using a MacBook Pro 2016 15". I had it running over an old hdd but decided to use a ssd because they are faster, but till now it didn't work. The ssd is new and fresh out of the box.

Oct 26, 2017 12:40 PM in response to Loner T

The complete output for diskutier list is this, the ssd is a SanDisk Ultra II. There is right now a Windows installation on it, which I installed using Rufus, which didn't work. It is formatted as NTFS and MBR. Thanks a lot for your help


/dev/disk0 (internal):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme 500.3 GB disk0

1: EFI EFI 314.6 MB disk0s1

2: Apple_CoreStorage Macintosh HD 499.3 GB disk0s2

3: Apple_Boot Recovery HD 650.0 MB disk0s3


/dev/disk1 (internal, virtual):

#: TYPE NAME SIZE IDENTIFIER

0: Apple_HFS Macintosh HD +499.0 GB disk1

Logical Volume on disk0s2

080C5A0B-2889-48D0-A5A3-264CE2D9E56E

Unlocked Encrypted


/dev/disk3 (external, physical):

#: TYPE NAME SIZE IDENTIFIER

0: FDisk_partition_scheme *240.1 GB disk3

1: Windows_NTFS CCSA_X64FRE_DE-DE_DV5 240.1 GB disk3s1

2: 0xEF 262.1 KB disk3s2

Aug 1, 2017 1:09 AM in response to dkhedstrom

dkhedstrom wrote:


I do not understand the double click on the .iso file. It just leads me to burning a disk. Where do I find "E:\sources\install.esd" ? There is something missing here. --DKH

If your ISO is already mounted, try install.wim instead of install.esd. Notice in step 1 that the goal is to mount the ISO, not Burn it. You can also mount it using diskutil.



User uploaded file

Aug 1, 2017 1:23 PM in response to Digitalclips

I have a 2017 MB Pro. I downloaded the apps, partitioned and formatted the USB drive. I selected the small FAT32 partition for the install by WinToUSB and the NTFS for the boot, seemed like the only choices. How and where do I add the Apple-specific drivers? You alluded to more comprehensive instructions for accomplish this installation, but I am unable to find the reference. --DKH

Nov 5, 2017 5:34 AM in response to Loner T

So I got it working now. But I figured a problem out. Its the sata III to usb c adapter. If I use the data III to usb 3.0 with an usb 3.0 to usb c adapter its working fine, but not with the direct connection which is kinda annoying since it would be much easier using it directly. Both adapters are the same brand and I know that the sata III to usb c adapter worked with my old hdd. I don't know what is causing the problem, if its just the adapter or if its software or other hardware.

But thanks so much for the help so far.

Nov 11, 2017 7:19 PM in response to LFGL

I've been running Windows from an external drive for some time. While I've technically have been able to get it to work with about any drive not all Windows software will work with such a setup. For example, Microsoft Visual Studio will not install on a drive that is reported as removable. And when the system drive is a removable drive it won't install at all. That said, for many other titles that I need to run on multiple machines this is a non-issue.


For instances when it is an issue I use a Windows2Go drive. I won't get into the technical details of exactly what makes a Windows2Go drive different than a regular USB drive. But with a Windows2Go drive Windows presents the drive to other software as a non-removable drive making that problem I encountered non-existant here. The drives work great, but they tend to be more expensive. I have a Western Digital Windows2Go hard drive (500 gigs), a Supertalent 128 GIG W2G drive, and another drive made to run Windows that also contains hardware encryption. Such drives are a lot more expensive but necessary for some scenarios.

Jun 10, 2016 6:06 AM in response to LFGL

I've posted this before but in less detail: This for Mac folks not familiar with using Windows commands (or would rather not). This is all done on the Mac until you actually boot into your new Windows USB.


For anyone with Parallels or VMWare Fusion it is extremely simple too. Get two free apps for Windows (I used the Mac to get them and download, to avoid crapware and then transferred the .exe once unzipped on the Mac to the Parallels.) The two apps are WintoGo (free) which uses an ISO of Windows 10 (or 8.1) to transfer to your USB3 attached external. I use an SSD and a $10 cable from Amazon. The other app you need to set up the drive without needing any knowledge what-so -ever about Bios etc. is called MiniTools Partition (free version) which allows you from Parallels to set the USB disk to MRB (essential) then partition the drive for the WintoUSB installation. Mac users are not familiar with all this stuff but two are required and it is like using Mac's own Disk Utils. You make two partitions, one small one, I use 200 MB (note that's MB not GB) and format as Fat32. Then the rest as NTSF. You then set the Fat32 partition as Primary and active then the NTFS one as active too. It all sounds complicated but it isn't really. All the options are simply there in the menus. The big difference with MiniTools Partition compared to Apple Disk Untilitiesis that it gets a little 'getting used to' in that every time to select an action, such as partition the 200 MB area, until you click the 'Apply' button nothing happens. If you do a few selections then click 'Apply' it does them sequentially. I prefer to apply each one as I go as sometimes options are not available unless the previous one is applied, e.g. you can't make a partition primary until it is formatted and so on.


I have several SSDs made this way and find a paid for utility on the Mac worth the $20, NTFS for Mac. This allows tou to mount multiple Windows bootable disks on the Mac desk top and have full read and write access. This means you can copy programs and data between then using the Finder on the Mac and not have to deal with Windows. I copy my entire Steam folder over for example. This saves hours of re-downloading.


Lastly AMD in May 2016 released Crimson Drivers for Macs running Windows. On my new Mac Pro I get full double GPU performance with AMD Catalyst now.


http://support.amd.com/en-us/download/desktop/bootcamp


Install this before anything else.


BTW I add a tild ~ in front of the AMD drivers folder in Bootcamp drivers (to prevent them even trying) if I install them later, as well as the Realtech driver folder. they both suck at time of writing. Windows installs better drivers itself. The only Apple drivers I use are the ones for the Apple keyboard. I bought a three button mouse too.

Run Windows 10 from an external SSD disk? Yes, it works!

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