I've been doing a lot of research about installing Windows on Mac - without having a MBR and such. I'm trying to create a pure GPT/EFI system without MBR. Currently, Mac Bootcamp creates a hybrid system which makes triple booting very difficult, and both double and triple booting very "kludge-ish."

Windows DOES support EFI install on GPT - it requires some terminal-doing on the windows install, but it can be done. please see here for a description of this. There are also lots of other posts supporting this.

However, Windows will only install to a UEFI 2.x. No Apple computers run on UEFI2.x, but rather an older, 1.x version of EFI.

My question is: Is there any way to update Mac's EFI to UEFI 2.x?


2 Answers 2


AFAIK, you can't upgrade a Mac's firmware to UEFI 2.x, and if you could, there's a good chance you'd have problems booting OS X from it.

You might be able to use a "software UEFI" implementation, such as UEFI DUET, on a 64-bit Mac. I wrote a Web page about this technique on conventional PCs. Since Macs look like such computers when they boot Windows via Boot Camp, there's a chance you could get that approach to work on a Mac; however, my limited understanding is that an MBR (regular or hybrid) is required to activate a Mac's BIOS compatibility mode, so this might be a wild goose chase. OTOH, maybe rEFIt could activate the BIOS mode if you put the UEFI DUET software on a different partition from the EFI System Partition.

If you want to try, I recommend installing the UEFI DUET software to an MBR USB flash drive. That might activate the Mac's BIOS support mode and enable the software to run correctly. If it does, you can experiment with installing Windows to a GPT disk (still using the flash drive to start up the UEFI DUET software) and then see if you can get the BIOS emulation to activate using just your normal GPT hard disk. If you can get UEFI DUET booting with the USB flash drive, it's likely you'll be able to get Windows installed on a pure GPT disk, but it's conceivable you'll be chained to the USB flash drive to boot Windows.

I'd like to emphasize, though, that this is very "bleeding-edge" stuff. You're as likely to trash your data as you are to get a working system out of it. Therefore, you should proceed only after you make complete backups and only if you fully understand and accept the risks.

  • Alright. That's unfortunate -- thanks a lot for the link to your page. It's some much-needed documentation on the technology.
    – kalaracey
    Jun 23, 2011 at 13:13

... No Apple computers run on UEFI2.x, but rather an older, 1.x version of EFI.

That's not really true @kalaracey—I was able to install Windows 8 in EFI mode on several Apple computers with year 2009 and later. Because Windows 8 needs UEFI 2.x firmware to load, all Apple iMacs newer then 2009 are for the most part (U)EFI 2.x based. On these machines you only have to change Apple’s special "hybrid MBR" GPT hard disk layout with a standard GPT "protective MBR"

Some interesting info from this Apple discussion page.

Thanks to Rod Smith at this point for his great GPT fdisk tool!

In summary, one can say regarding Windows EFI installation:

  • iMac 2007 & 2008: 64bit firmware but EFI 1.x based, Windows 8 install media freezes when selected at startup

  • iMac 2009 & later: 64bit firmware and mostly (U)EFI 2.x based, Windows 8 install media loads fine at startup

It would be interesting to know if it's possible to create a sort of "EFI 2.x to EFI 1.x wrapper" for these 64bit but EFI 1.x based iMac machines. Perhaps it is then possible to load Windows 8 UEFI setup?

  • 1
    DUET is already providing such features (even though it may not be as streamlined as an actually "dedicated" wrapper). But put that aside, it seems like Itanium Windows Servers builds used to support EFI 1.10. And even if that's not directly usable on x86, there are plenty of people trying to take advantage of that.
    – mirh
    Dec 25, 2019 at 21:51

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