Windows 8 UEFI on iMac7,1 (mid 2007 iMac)

Discussion in 'Windows, Linux & Others on the Mac' started by unionaire, Aug 9, 2012.

  1. unionaire macrumors newbie

    Joined:
    Jan 19, 2012
    #1
    Okay it seems like it is a generally accepted idea that windows 8 will boot in UEFI mode natively in all INTEL Macs, but I have to say otherwise because I personally encountered this strange problem and does not know how to proceed.

    Here's my story and please help if you have the same machine/problem.

    I have two iMacs at home, one is iMac7,1 (mid 2007 iMac), and the new one is iMac 12,2 (2011 iMac).

    So Windows 8 is now approaching and I was trying to install it to both iMacs. Since the 2011 iMac is my work station now I try to experience the system on my old machine, the 2007 Mac.

    So I formatted one of my USB drive as GUID, and get a FAT32 partition, and placed the WIN8 ISO content on it. It is a working USB drive because it boots nicely into the installer in iMac12,2, however, it simply hangs in iMac7,1, at /eft/boot/bootx64.efi, keep the computer on for half an hour nothing changes. Whether I call it with the native bootloader in Mac (the one you pressed and hold Alt), or rEFIT won't change a thing, it just hangs in the same place with same message.

    I also tried recording a DVD from ISO image, and format the internal hdd as GUID (wipe bootcamp), and place the DVD content in the internal hdd to boot, but stuck in the same place.

    I know it is something special about this particular model of iMac that stops windows 8 from booting into UEFI mode, but I had no idea what that "specialty" is, and I hope you guys can enlighten me with some better ideas.

    The other purpose of this thread is to bring about one additional thing to the forum so that other people can benefit from this (I think), that not all Macs are the same when it comes to issues like this. It is somehow hardware related, and specific to each model.

    For example, most (if not all) intel Mac guys probably know about this fact that intel Macs cannot boot off MBR bootable drives from a external USB source, it can only boot from a CD. Installing windows on ordinary PC almost never requires burning any CD/DVD any more by using USB drives, but for Macs, we usually still have to rely on DVD (not sure if it is intentionally done by Apple to make windows look really dumb and outdated). However, there are cases where people report that USB MBR bootable drive works just for them, it is rare but I've definitely seen this guy saying that it works like charm for him in his Macbook or Macbook pro (sorry I forgot the name but I'm sure some of you have heard of the same story).

    That and my story here shows that no two Mac models are the same, what works for 1 probably won't work for the other, so I suggest that when we say we had a success on something (especially windows related issues), we'd better also explain the setup we have, so other people can benefit from it.

    For me I'm sharing this information hoping that I can get a solution from you guys, if not at least people who own the same machine and/or with the same problem can save sometime trying.:)

    BTW it's probably something related to the firmware of the iMacs, but for 2007 iMac there's no more updates coming so it will probably never be solved unless we can get pass this.
     
  2. murphychris macrumors 6502a

    Joined:
    Mar 19, 2012
    #2
    It could be either an EFI bug or a bootloader bug, or both.

    I have done quite a bit of testing for the Fedora Project to get Fedora linux to boot in EFI mode on Macs instead of depending on the CSM-BIOS (and the commensurately flaky and risky hybrid MBR that it requires). And each Mac's EFI behaved slightly differently.

    The state of EFI is something in the realm of a cluster|*ck of bugs. It's an immense pile of largely untested code. Apple's implementation is the oldest, still based on Intel EFI 1.10 according to all the firmwares I've looked at, with some minor bits of UEFI 2.x (primarily GOP). And that's just official differences at the specification level; the implementation differences are locating lots and lots of UEFI bugs.

    What is the message? I'd forward it to Microsoft as a bug report if you can, with as much information about the failing computer, and at the end of the bug report add "Regression" and point out that on alternate hardware (which you should specify the details of) the problem does not occur. I'd do the same with Apple and then cross reference the bugs. I don't know if it's in either of their interests to fix this, but worth a shot.

    I'd say that it's most likely firmware related.

    An apparent limitation of the CSM. However, some models expose a feature in Boot Camp Assistant to build a USB bootable Windows install disk. So somehow they're getting around this for installs, although I don't know how as I haven't inspected such a USB stick.

    Oh surely Apple wouldn't ever do that. :)

    Actually, Apple's EFI doesn't mind booting off USB MBR disks at all. In fact you can using an MBR only partition scheme, format a partition JHFS+, and Mac OS X cloned to that partition will happily boot all day long. It's just that the Mac OS X installer will refuse to install to an MBR disk.

    So it's possible these people actually are EFI booting from these USB MBR media, not CSM-BIOS booting.

    I think it may be unsolvable. I'd still file the bugs. The more Apple is aware people understand the problem, perhaps the better chance 2012 hardware will not be forever crippled in a similar manner.

    But then, it may be in Apple's interest to forego UEFI entirely, as maybe it makes it easier to VM Mac OS X on non-Apple hardware. Or perhaps they make a leap to UEFI 2.3.1+ which is the first UEFI supporting Secure Boot, and they require only signed bootloaders: out of the box that would be Windows and Mac OS only. So our OS choice could become even more constrained than it presently is.
     
  3. unionaire thread starter macrumors newbie

    Joined:
    Jan 19, 2012
    #3
    Hi murphychris,

    Thanks for the detailed reply.

    The message it hangs at is :
    Code:
    Starting
    /efi/boot/bootx64.efi ...
    
    Something like that, and it just doesn't move forward, doesn't spit out an error or anything. If it were bootmgr.efi (win7 efi) it will say something about unsupported efi.

    Yes, about Mac booting off MBR disk, my mistake I did not make it clear, it is actually not booting windows off MBR external disks other than CD/DVD media. Then I don't really know much about booting other than Windows so I wouldn't have made it more clear, but I hope you understand what I meant.

    It was just frustrating that couple months back I heard that WIN8 will work under EFI with Macs, and now I found that it's only partially true. Whatever the case, I really hate how we now have huge harddrives and can't install as many OSs as we want and run them as fast as they could. Well at least it works on the newer Macs I suppose.
     
  4. murphychris macrumors 6502a

    Joined:
    Mar 19, 2012
    #4
    So the UEFI spec proposes a default bootloader location which is /efi/boot/bootx64.efi. The idea is that every vendor has their own directory and bootloader file, and there'd be an EFI setup where you'd see the available bootloaders and choose them. Apple doesn't offer us such a thing, and some other vendors also choose to not have user selectable bootloaders. So a default one is needed that's always honored, and that's the /efi/boot/bootx64.efi

    I bet if you do a diff on that bootx64.efi and bootmgr.efi that you end up with the same binary.

    Performance with CSM booting should be the same, albeit slightly delayed at the beginning. The bigger issue is the lack of full power management so it appears Windows has crappy battery life compared to Mac OS X, but mostly this has to do with how the OS is being booted.

    But for large disk support, it's true beyond 2TB we need to UEFI boot Windows and right now that's non-trivial for a lot of people.
     
  5. murphychris macrumors 6502a

    Joined:
    Mar 19, 2012
    #5
    Actually I'm not sure we fully get AHCI support with CSM boots either, which might negatively impact SATA performance somewhat. But I don't have any benchmarks. It may limit SSD more noticeably than HDD.
     
  6. unionaire thread starter macrumors newbie

    Joined:
    Jan 19, 2012
    #6
    Yes, I know for a fact that bootx64.efi and bootmgr.efi are the same stuff.

    Whatever the case it's stupid how the .efi loading mechanism is programmed, at least from consumer's perspective.
     

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