Windows 10 64 bits on external drive

[Nguyen Duc Hieu]

I tried to install and use Windows 10 64bit on an old iMac. The process is as following:
1) On the PC
- Download Windows ISO (I used an old version 1803 build)
- Use Rufus to install WindowsToGo on an SATA to USB 3.0 box. (I used a Sandisk SSD)
- Reboot and updates windows on the PC.

2. Moved to iMac No.1 (24" early 2009 A1225, OS X Elcapitan)
- Boot to OSX
- Reboot to Windows (System preference)
- Install BootCamp 6 for all drivers
- Install some more drivers from BootCamp 4
- Reboot several times to make sure all things worked fine.

3. Move the drive to iMac No.2 (27' mid 2010 A1312, OS X High Sierra)
- Boot to OS X
- Reboot to Windows (on external drive) (via System Preference)
- The iMac switched to boot from the USB, but then it stuck at a black screen with a note: "No Bootable device found...."
- I had to turn-off the iMac, do PRAM reset
- It boot back to OSX as normal
But when I tried to boot from the external disk, it stuck again at the boot screen.

Could you suggest any thing I can do to make it works?

I would like to put the SSD with Windows 10 pre-install to the iMac when I open it, it may work as an internal drive as it has been working well when installed in my Mac Pro 1,1. But until then, I would like to try to make it work from an external drive and have a fully functional SSD when I open the iMac to put it in.

 

[Nguyen Duc Hieu]

I guess the error was in the disk partition type.

I partitioned the SSD in MBR. Therefore on iMac 2009 it worked, but failed to work on iMac 2010.

I will reinstall the WindowsToGo with GPT partition and report the result here.

 

[joevt]

You could probably make a Windows that boots using either option: legacy BIOS or EFI.
Make a hybrid MBR/GPT disk.

Hybrid MBRs

You can use gdisk or iPartition to set that up.

Then use the Windows installer to fix up the MBR boot or the EFI boot (whichever is missing).

 

[DaveFromCampbelltown]

I formatted my external drive for Windows using diskutil

1. Use 'diskutil list' (minus quotes) to identify the drive you want to reformat
2. Use 'sudo diskutil partitionDisk disk(xx) GPT jhfs+ Win10 100%' to re-partition the whole drive as a GPT disk.

'disk(xx)' is the drive number of your disk.
For example, if you get --

/dev/disk4 (external, physical):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *500.1 GB disk4
1: EFI ⁨EFI⁩ 209.7 MB disk4s1

then you would use 'sudo diskutil partitionDisk disk4 ...'
It doesn't matter that you are formatting it as 'jhfs+' (Mac format) as it will be re-formatted anyway, and the volume name 'Win10' will get overwritten anyway. 100% means that you are going to use the whole drive.
Remember to use the uppercase D in 'partitionDisk' otherwise it won't be accepted.

I used Hasleo WinToUSB to set up Windows on the external drive.

Before you start, remember to use Boot Camp Assistant to download the Windows Support Software and copy it to a FAT32 formatted thumb drive. As soon as you get Windows up and running on your Mac, install that software.

 

[Nguyen Duc Hieu]

I rebuilt the SSD using Rufus, this time with GPT partition.
The result was the same: It still stuck at the black screen, one flickering slash under the notification: "No bootable device found - Insert a disk and hit any key...."

I'll try Hasleo tonight to see if it makes any difference.

If even Hasleo fails, maybe I'll try to clone High Sierra on the external drive to see if the problem lies in the communication between iMac and the USB box itself.

 

[joevt]

"No bootable device found" means you are trying to boot using legacy BIOS boot but none of your partitions have legacy BIOS boot code in the MBR partition.
Maybe legacy BIOS boot can only work for internal drives (except for Windows install media?)
Maybe the iMac is too old to support EFI boot of Windows.

Attached is a script to dump all the info about your partitions.
sudo ./dumpvols.sh > dumpvols_result.txt 2>&1

Edit: script moved to https://gist.github.com/joevt/a99e3af71343d8242e0078ab4af39b6c

 

[Nguyen Duc Hieu]

Yesterday, when I clone the internal disk (OS X High Sierra) with the external one, booting was fine.
So the only option now for me is the hybrid mode for Windows.
It was so easy on the iMac early 2009, that I almost forgot that every Mac are different...