Bootcamp - Windows 10 - No bootable device -- insert boot disk and press any key

Question

I have got a problem with booting into Windows 10 after changing Superdrive to SSD - "No bootable device -- insert boot disk and press any key". It works if i leave only old hard drive, removing the new SSD, the Windows boots well.

The boot option screen can detect old MacOS, new MacOS and the partition with Windows on old HD.

The primary OS is on SSD /dev/disk0 and the Windows in on HD /dev/disk1s4.

$ diskutil list
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD SSD        499.2 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3

/dev/disk1 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *750.2 GB   disk1
   1:                        EFI EFI                     209.7 MB   disk1s1
   2:                  Apple_HFS Macintosh HD            599.3 GB   disk1s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk1s3
   4:       Microsoft Basic Data                         150.0 GB   disk1s4

$ sudo fdisk /dev/disk0
Disk: /dev/disk0    geometry: 60801/255/63 [976773168 sectors]
Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 1: EE 1023 254  63 - 1023 254  63 [         1 -  976773166] <Unknown ID>
 2: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
 3: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
 4: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
$ sudo fdisk /dev/disk1
Disk: /dev/disk1    geometry: 91201/255/63 [1465149168 sectors]
Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 1: EE 1023 254  63 - 1023 254  63 [         1 -     409639] <Unknown ID>
 2: AF 1023 254  63 - 1023 254  63 [    409640 - 1170501216] HFS+        
 3: AB 1023 254  63 - 1023 254  63 [1170910856 -    1269536] Darwin Boot 
*4: 07 1023 254  63 - 1023 254  63 [1172180992 -  292966400] HPFS/QNX/AUX

Mac OS: Sierra, 10.12.6 HW: MacBookPro Mid 2012

I've read tons of similar topics, but unfortunately wasn't able to figure out the fix. I really hope someone can advise.

Thank You.

Answer 1

Install the Windows boot files to the SSD. This takes about 100 MB of space.

Basic steps are given below. (Not necessarily in this order).

1. Create a Windows installer bootable flash drive.

   Note: This usually is easier to create when the firmware updates included with High Sierra or newer versions of macOS have been installed.

2. Shrink the disk0s2 on the SSD and create a 100 MB ExFAT partition.

3. If necessary, change SSD to hybrid partitioning.

4. Boot from the Windows installer.

5. Open a Command Prompt window.

6. Use the diskpart command to format the Windows partition on the SSD. and make this partition active.

7. Install the boot software to the MBR, VBR and Windows partition on the SSD. For the MBR and VBR use the bootsect command. For the Windows partition, use the bcdboot command. Have the boot software installed so Windows can reside on the HDD.

   Note. The Volume Boot Record (VBR) refers to the first sector of the Windows partition you wish to BIOS boot from. Actually, this boot software may cover more than just the first sector.