The ultimate way to install Windows 8.x in (U)EFI mode on Apple systems

Is this easy as i'm not real good with the terminal and fdisk. If you could give a step by step I would be greatful!! Ted

Today I followed this recipe exactly to add Windows 8.1 to a 13 inch Retina, Late 2013. My reason for wanting to go this route and keep the disk purely GPT was in order to have three visible partitions: one OSX, one Windows, and one exFat Data.

Windows installed flawlessly with zero fuss. I've restarted the system several times in both operating systems and made various updates. Everything is going fine so far, and I can access all three partitions from either OS.

It might be worth mentioning that I created a USB Windows boot disk using method 3 provided here:

http://tipsandtricksforum.com/thread-245.html

I then added the boot camp drivers by downloading and following the directions here:

Boot Camp Support Software 5.1.5640

I guaranteed that the Windows boot disk would only boot in EFI mode by following the directions here:

http://technet.microsoft.com/en-us/library/dn293283.aspx

Once I began installing Windows, I had to format the partition I'd created for it. (I had just made it exFat for the time being when I created it in Disk Utility.) Other than that, it was a completely straightforward, out of the box Windows install. (No need to hold down the alt key on reboots, or any of that.) Once the installation was finished, I ran Setup from the Boot Camp folder on my USB boot disk to get all my drivers in place.

I noticed that running setup for the boot camp drivers changed the name of my Windows partition to BOOTCAMP. I was afraid it might have messed with my MBR as well. I checked with gdisk, and confirmed that the disk is still GPT with protective MBR. -- For anyone wondering what all that mumbo-jumbo means, it's what you need in order to have more partitions than just Macintosh HD and BOOTCAMP.

Awesome. Thanks lion10.

Is there another option to boot up Windows 8.1 (x86 or x64) installation media on EFI 1.1 Macs?

You only have two methods, EFI (which does not work correctly on Macs prior to Late 2013 models) or BIOS (aka Hybrid MBR) on older Macs. Virtualization engines provide a different path without partitioning.

Thanks for your input!

BTW Is there any way to modify the contents of the Win 8.1 installer ISO so that it boots up in EFI 1.1 or BIOS so it can used to install Windows on an early 2008 8,1 iMac or earlier?

I have tried a number of different things and so far the only thing that has worked is to install Win 8.1 x64 in a VM. I was really wanting to install it in a partition, to maximise performance. Unless I can modify the Win 8.1 installer then my only other option (besides using a VM) is to use bootcamp to create a Windows 7 x86 partition (or possibly an x64 partition if I can fool bootcamp) and run the relevant x86 or x64 Win 8 installer from within Win 7.

Hi lion10 / yujyufudan,

Once install Windows this way how to switch between them ? Is it by pressing Option key at bootup ?

Hey i dont get step 3:

"Start Windows 8 setup in EFI mode; - switch to "Windows prompt" under "repair tools". Start command diskpart. Check your partition; - select that one with name "EFI". Add the drive letter "b" with the command assign letter=b. (Note, this point is perhaps not needed at some systems.)"

how do i switch to Windows prompt? Do i have to press something when booting the usb Stick? i can just see install :/

T0m93 wrote:

Hey i dont get step 3:

"Start Windows 8 setup in EFI mode; - switch to "Windows prompt" under "repair tools". Start command diskpart. Check your partition; - select that one with name "EFI". Add the drive letter "b" with the command assign letter=b. (Note, this point is perhaps not needed at some systems.)"

how do i switch to Windows prompt? Do i have to press something when booting the usb Stick? i can just see install :/

You need to run Windows Installer in EFI Mode and then click on Repair once the installer starts. One option in Repair Tools is Windows prompt (aka command prompt). On older Macs this can cause your GPU, Audio to not function properly.

Well it worked with shift f10. And some how i Managed to Type in the right commands and Assisi efi=b, but when i tried to install win 8.1 it says: i should convert the EFI drive from nfts into fat32. I dont really know What to do 😀 Anybody had this before? (MB pro late 2011 with fusiondrive)

EFI installation require a MSR (Microsoft Reserved) and a separate NTFS (MSD) partition. Typically the partition is formatted as a Free Space, which allows the EFI Installer to carve out a 128MB MSR and the remainder goes to the NTFS partition.

Ok. Hmm does anyone know how i can convert a Partition into free Space. I got Fusion Drive and cant delete it (Partition is from SSD not from the Fusion Drive). Is there any Terminal command?

And the win8 setup created around 6 new 100-300MB Partitions by now. Does anyone know how i can get them all back together? Hopefully i will get this to work some how 😀

Please post the output of

diskutil cs list

sudo gpt -vv -r show /dev/disk0

sudo gpt -vv -r show /dev/disk1

Every failed attempt at EFI install creates an MSR and fails, leaving the MSR hanging.

I just deleted all Partition in the Windows 8 setup---> Had my previous Partition back. I Just had to delete the EFI Partition too... It was too easy :/ It worked finally after didnt know he could recreat the EFI PArtition 😀 But WIN 8.1 is running and Im happy and this Guide is awesome. By the way i had already 14 ne Partitions from failed Setups 😁

Output Disk0 (where the Partiton is located):

gpt show: /dev/disk0: mediasize=256060514304; sectorsize=512; blocks=500118192

gpt show: /dev/disk0: PMBR at sector 0

gpt show: /dev/disk0: Pri GPT at sector 1

gpt show: /dev/disk0: Sec GPT at sector 500118191

start size index contents

0 1 PMBR

1 1 Pri GPT header

2 32 Pri GPT table

34 2014

2048 262144 1 GPT part - E3C9E316-0B5C-4DB8-817D-F92DF00215AE

264192 156395520 2 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

156659712 343196296 3 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC

499856008 262144 4 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

500118152 7

500118159 32 Sec GPT table

500118191 1 Sec GPT header

Toms-MBP:~ Tom$

I Think its all Fine again 🙂 But Thanks Any way. Great Guide 😀