Windows Boot Manager issue with Dual Boot on different Hard Drives

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  1. Posts : 22
    Windows 10 x64 UEFI
    Thread Starter

    Sorry, my Win7 system is in French.
    Disk 0 is my SSD with Win7 64
    Disk 1 is my Toshiba 4TB
    Disk 2 is my Seagate 2TB
    Windows Boot Manager issue with Dual Boot on different Hard Drives-capture.png
      My Computer

  2. Posts : 4,523
    Windows 11 Pro 64-bit

    You have not post the screenshot for List Volume command.
      My Computer

  3. Posts : 22
    Windows 10 x64 UEFI
    Thread Starter

    Sorry about that (old habits)

    Windows Boot Manager issue with Dual Boot on different Hard Drives-capture.png
      My Computer

  4. Posts : 4,523
    Windows 11 Pro 64-bit

    You will have to use Diskpart command to find out the System Reserved partition drive letter.
    The output of the below commands may display the name of the System Reserved partition as only System or EFI.

    Type diskpart and press Enter.
    Type list volume and press Enter.

    Under the label (Info) row, find the label System Reserved and note its corresponding Volume number.

    Now type select Volume=N and press Enter, where N is the Volume number you noted earlier.
    Now type assign letter=w and press Enter.
    Type exit and press Enter.
    Type bcdboot C:\Windows /s w: /f ALL and press Enter.

    Please replace partition letter C: with Windows installed partition letter. When computer boots into Windows Recovery Environment (WinRE) environment the drive letter assign to Windows partition may not be C: drive letter because Windows 7, 8 , 8.1 and 10 creates a separate system partition when it's installed from scratch. The system partition contains boot files WinRE assigns the system partition the C: drive letter and the Windows installed partition will be assign any other drive letter usually D: drive letter is assign to Windows installed partition. The Bcdedit /enum | find "osdevice" command can be use to find out the drive letter of the Windows installed partition the output of the Bcdedit command is similar to this osdevice partition=D:. The drive letter after partition= is the drive letter of the Windows partition.
      My Computer

  5. Posts : 2,790
    Linux Mint 20.1 Win10Prox64

    There are some misleading information in this thread.
    1. Unlike Legacy MBR BIOS. When running Windows using GPT style partition, The UEFI firmware will update the boot configuration accordingly.
    2. For each Windows using GPT with separate EFI System partition, You will have a separate "Windows Boot Manager" ie. you will have one for Windows 7 and one for Windows 10.
      NOTE: You must first connect the SSD/HD then restart or turn off the PC then turn on the PC for UEFI firmware to update the boot configuration.

    There is nothing wrong with your Windows 7/10 booting. You just need to set your UEFI firmware to point to the correct "Windows Boot manager" and and set the SSD/HD to be the first boot device. Or using the Boot Menu for a one time boot.

    It is hard to visualize how it works. So here's some screen shot from my PC.
    From Disk Management: I have 2 Windows installed, 1 on disk 0 (Connect to Sata 0) and the other on disk 3 (Connect to Sata 5). On disk 2, I have 2 WinPE's (WinPE does not have Windows Boot Manager)
    Windows Boot Manager issue with Dual Boot on different Hard Drives-p4.jpg
    For one time boot from boot menu, I just have to select which one to boot from. Note that the 2 "Windows Boot Manager" associated to 2 different SSD ID's. #1 is for Windows on Disk 0, #2 is for Windows on Disk 3. #3 &#4 are for 2 WinPE's
    Windows Boot Manager issue with Dual Boot on different Hard Drives-p0.jpg
    For normal boot. On the next 3 screens, you'd have to select which "Windows Boot Manager" to boot from and also the appropriate SSD/HD.
    Windows Boot Manager issue with Dual Boot on different Hard Drives-p3.jpg
    Windows Boot Manager issue with Dual Boot on different Hard Drives-p1.jpg
    Windows Boot Manager issue with Dual Boot on different Hard Drives-p2.jpg

    NOTE: The GUI on my MB looks different from your MB but all options are there. In addition, If you disconnect your HD (Windows 10) then you would have to go back and reset the boot order again.
      My Computer

  6. Posts : 4,523
    Windows 11 Pro 64-bit

    The following diagram illustrates some of the key portions of the process that the Boot Manager follows after it is launched by the UEFI environment.

    Important thing to understand: many UEFI firmwares implement some kind of BIOS compatibility mode, sometimes referred to as a CSM. Many UEFI firmwares can boot a system just like a BIOS firmware would – they can look for an MBR on a disk, and execute the boot loader from that MBR, and leave everything subsequently up to that bootloader.

    Unlike BIOS, UEFI certainly does understand, to varying degrees, the concepts of ‘disk partitions’ and ‘bootloaders’ and ‘operating systems’. Instead of the firmware only knowing about disks and one ‘magic’ location per disk where bootloader code might reside, UEFI has much more infrastructure at the firmware layer for handling boot loading.

    The UEFI spec defines an executable format and requires all UEFI firmwares be capable of executing code in this format. When you write a bootloader for native UEFI, you write in this format.

    An ‘EFI system partition’ is really just any partition formatted with one of the UEFI spec-defined variants of FAT and given a specific GPT partition type to help the firmware find it. . Instead of having to write bootloader code to the ‘magic’ space at the start of an MBR disk, operating systems and so on can just create, format and mount partitions in a widely understood format and put bootloader code and anything else that they might want the firmware to read there.So if you are writing an OS or something else that you want to run on any UEFI compliant firmware, this is why the EFI system partition concept is so important: it gives you (at least in theory) 100% confidence that you can put an EFI executable on a partition formatted with the UEFI FAT implementation and the correct GPT partition type, and the system firmware will be able to read it. This is the thing you can take to the bank, like ‘the firmware will be able to execute some bootloader code I put in the MBR space’ was in the BIOS world.

    The firmware will look through each EFI system partition on the disk in the order they exist on the disk. Within the ESP, it will look for a file with a specific name and location. On an x86-64 PC, it will look for the file \EFI\BOOT\BOOTx64.EFI. What it actually looks for is \EFI\BOOT\BOOT{machine type short-name}.EFI – ‘x64’ is the “machine type short-name” for x86-64 PCs. The other possibilities are BOOTIA32.EFI (x86-32), BOOTIA64.EFI (Itanium), BOOTARM.EFI (AArch32 – that is, 32-bit ARM) and BOOTAA64.EFI (AArch64 – that is, 64-bit ARM). It will then execute the first qualifying file it finds (obviously, the file needs to be in the executable format defined in the UEFI specification).
      My Computer

  7. Posts : 4,224
    Windows 10

    Hey Freebooter! Nice diagram and explanation. Can you please provide a link to its source? Thanks,
      My Computers

  8. Posts : 4,523
    Windows 11 Pro 64-bit

    There is no url link.
      My Computer


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