Daniel miller

Q: El Cap won't dual boot Windows 8.1 w/ EFI

I have a 2009 Mac Pro. Upgraded the procs to dual x5690 and "flashed" it to read as a 5,1. Running a GTX 980 and Quadro K4000. 64 Gb ram. OSX installed on a owc pcie ssd, Windows installed on Samsung 850 pro plugged into spare sata connector in optical bay.

 

 

My quandary: I was running Yosemite and Windows 8.1 in harmony. Each one on its own drive, not two partitions of the same drive. I upgraded to El Cap. I could no longer boot into Windows if my El Cap drive was plugged in. I did some research and saw that El Cap doesn't like MBRs so I did a clean install of Windows after switching it over to EFI but it still won't boot. I use startup disk utility, and it reboots and just sits on a black screen.

 

 

Is there a way to get this sorted? Do I have to disable this new SIP feature that seems to be wreaking havoc on all sorts of folks? Help me Obi-Wan Kenobi....

Mac Pro, OS X El Capitan (10.11.1), Windows 8.1

Posted on Dec 11, 2015 9:51 AM

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Q: El Cap won't dual boot Windows 8.1 w/ EFI

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  • by Loner T,

    Loner T Loner T Dec 19, 2015 6:55 AM in response to Daniel miller
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    Dec 19, 2015 6:55 AM in response to Daniel miller

    With this configuration, can you check the OS X disk EFI for Microsoft directories?

  • by Daniel miller,

    Daniel miller Daniel miller Dec 19, 2015 8:15 AM in response to Loner T
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    Dec 19, 2015 8:15 AM in response to Loner T

    Loner T wrote:

     

    With this configuration, can you check the OS X disk EFI for Microsoft directories?

     

    Yes, its has the same directories as before:

     

    Boot > bootx64.efi

    Microsoft > boot > lots of files & folders

  • by Loner T,

    Loner T Loner T Dec 19, 2015 9:49 AM in response to Daniel miller
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    Dec 19, 2015 9:49 AM in response to Daniel miller

    With both disks connected, if you run BCA and remove Windows, does the EFI partition still contain the Microsoft directories? If yes, we can mount the EFI partition from the OS X disk, and remove the Microsoft tree, and re-install Windows with both disks connected using EFI Boot and check if the BCD is corrected.

  • by Daniel miller,

    Daniel miller Daniel miller Dec 20, 2015 10:33 AM in response to Loner T
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    Dec 20, 2015 10:33 AM in response to Loner T

    Ok, Windows drive is wiped. The Microsoft tree still exists on the OS X Disk. When you say "remove" is there a special procedure I should follow? or just delete the directory and empty trash?

  • by Loner T,

    Loner T Loner T Dec 20, 2015 12:13 PM in response to Daniel miller
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    Dec 20, 2015 12:13 PM in response to Daniel miller

    You can mount the EFI partition and remove the Microsoft directory and all it's sub-directories. I suggest you backup the EFI directory before you delete anything to be extra safe.

  • by Daniel miller,

    Daniel miller Daniel miller Dec 26, 2015 11:31 AM in response to Loner T
    Level 1 (5 points)
    Dec 26, 2015 11:31 AM in response to Loner T

    Still no luck. I think I'm going to have to throw in the towel. upon re-installing Windows AGAIN, it still won't write an EFI partition on the Windows drive if the OS X drive is plugged in.

     

     

    Heres the output from diskutil list

    /dev/disk1 (internal, physical):

       #:                       TYPE NAME                    SIZE       IDENTIFIER

       0:      GUID_partition_scheme                        *512.1 GB   disk1

       1:         Microsoft Reserved                         134.2 MB   disk1s1

       2:       Microsoft Basic Data BOOTCAMP                512.0 GB   disk1s2

     

    Unless there is a way to brute force this into existence (manually create the EFI partition in windows od OS X DU, and then somehow get the files that are supposed to be there and place them there manually. This is super annoying. It worked 100% of the time before. Why did they change it....

  • by Loner T,

    Loner T Loner T Dec 26, 2015 12:26 PM in response to Daniel miller
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    Dec 26, 2015 12:26 PM in response to Daniel miller

    Can I suggest the following? If you notice, since there is no EFI partition, BCA cannot use it, so it points to the one it can find, which is on the OS X drive.

     

    1.  Erase this disk using Disk Utility and check if you see an EFI Partition.

    2. If you do not, remove all internal disks, boot from an external OS X disk (you may have to install OS X on an external disk first).

    3. Erase this Windows disk, and check if you get an EFI Partition.

    4. If you are able to create a standard EFI, then try installing Windows on this disk, by making the entire disk (as Free Space).

  • by Daniel miller,

    Daniel miller Daniel miller Dec 27, 2015 11:37 AM in response to Loner T
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    Dec 27, 2015 11:37 AM in response to Loner T

    I've tried that. It seems that if OS X writes the EFI partition Windows will not recognize it as such, and it will create a second EFI partition. So I end up with 2. 1 that is 200 MB created by OS X and 1  that is 100 MB created by the Windows Installer. Then it keeps telling me that Windows can't be installed on this disk, check the log.

     

    I check the log, and can't figure out what it doesn't like about the drive....

    IMG_0036_r.jpg

     

    It only seems to work with the OS X drive attached is if I got into diskpart and do clean and convert gpt

     

    If I do anything else, it doesn't work. However, when I installed it before and removed the OS X disk, it at least had an EFI partition. Would it be possible to install Windows with the OS X drive removed, and then just place whatever files are supposed to be there in the partition manually?

  • by Loner T,

    Loner T Loner T Dec 27, 2015 11:49 AM in response to Daniel miller
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    Dec 27, 2015 11:49 AM in response to Daniel miller

    Yes, but you will also need Windows Startup Repair after you move the files.

  • by Daniel miller,

    Daniel miller Daniel miller Dec 27, 2015 12:18 PM in response to Daniel miller
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    Dec 27, 2015 12:18 PM in response to Daniel miller

    So if I can get the MSR and EFI partitions both written, and windows installed, we should be able to get this working.... Alright, ill check back in after I try this again

  • by Daniel miller,

    Daniel miller Daniel miller Jan 8, 2016 10:44 AM in response to Loner T
    Level 1 (5 points)
    Jan 8, 2016 10:44 AM in response to Loner T

    It's been a while, I know. The Christmas break really threw things into a mess. At any rate, I think I'm close to having this set up correctly. Let me break down where I'm at.

     

    I got Windows installed a while back, and have a project that I need to do some work on, so I didn't want to re-install AGAIN and then re-install all my programs. SO:

     

    1. using disk manager I shrunk my Primary Partition by 300 MB ( control panel > system & security > administrative tools > computer management > disk management > right click on desired Primary Partition > shrink partition)

     

    2. Using diskpart I made a 200 MB EFI partition(command "create partition efi size=200")

     

    3. Using disk part I ensured that the new EFI partition was selected. ( command "list partition" > see partition number of desired partition in this case partition 3 > command "select partition 3")

     

    4 Using diskpart I formatted that partion to FAT32 (command "format quick fs=fat32 label=WINDOWS")

     

    5 Using disk manager I checked the new partion. It tells me I have a 200 MB Healthy EFI partition.

     

    6 Booted into El Cap

     

    7 Using terminal command "diskutil list" I saw that the EFI partion on my Windows disk was disk01s3

     

    8 I mounted the EFI partition using the commands you mentioned in the other thread:

    sudo mkdir -p /Volumes/EFI

    sudo mount -t msdos /dev/disk0s3 /Volumes/EFI

     

    9 Noticed that partition now has an folder structure: "EFI > APPLE > EXTENSIONS > Firmware.scap"

     

    It still won't boot into Windows without holding the option key, but I think I am close. Should the EFI be partition 0 or partition 1? OR do I need Windows Startup Repair to point the boot mngr to the new EFI partition on the Windows disk?

  • by Loner T,

    Loner T Loner T Jan 8, 2016 11:32 AM in response to Daniel miller
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    Jan 8, 2016 11:32 AM in response to Daniel miller

    Was this partition created on the Windows disk?  Can you post the output of diskutil list for this disk, similar to the disk1 output you posted previously? Is there a Microsoft directory on your OSX disk? If yes, you need to repair/rebuild the BCD on this new EFI partition on the Windows disk.

  • by Daniel miller,

    Daniel miller Daniel miller Jan 8, 2016 11:34 AM in response to Loner T
    Level 1 (5 points)
    Jan 8, 2016 11:34 AM in response to Loner T

    Loner T wrote:

     

    Was this partition created on the Windows disk?

     

    Yes

     

    Loner T wrote:

     

    Can you post the output of diskutil list for this disk, similar to the disk1 output you posted previously?

     

    Well, it's since renumbered itself to disk0, but here is the output

    #:                      TYPE NAME                    SIZE      IDENTIFIER

      0:      GUID_partition_scheme                        *512.1 GB  disk0

      1:        Microsoft Reserved                        134.2 MB  disk0s1

      2:      Microsoft Basic Data BOOTCAMP                511.7 GB  disk0s2

      3:                        EFI WINDOWS                209.7 MB  disk0s3

  • by Loner T,

    Loner T Loner T Jan 8, 2016 11:38 AM in response to Daniel miller
    Level 7 (24,307 points)
    Safari
    Jan 8, 2016 11:38 AM in response to Daniel miller

    Yes, you need to repair/rebuild the BCD on this new EFI partition on the Windows disk.

  • by Daniel miller,

    Daniel miller Daniel miller Jan 8, 2016 11:43 AM in response to Loner T
    Level 1 (5 points)
    Jan 8, 2016 11:43 AM in response to Loner T
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