Windows 8 and USB booting

Discussion in 'Mac Pro' started by ScottishCaptain, Dec 27, 2012.

  1. macrumors 6502a

    Joined:
    Oct 4, 2008
    #1
    I haven't seen this confirmed anywhere, so I figured I'd be the first one to do it here incase anyone else is searching for a relevant answer.

    If you follow this guide to the letter:

    http://tweaks.com/windows/52279/how-to-create-a-windows-to-go-usb-drive/

    Windows 8 is capable of booting natively, from EFI, on the Mac Pro. This means that the EFI partition shows up as "EFI Boot" under the OS chooser (holding the ALT key when you reboot), and you can select it and boot Windows 8 from an external device.

    Everything works OOTB on the 2010/2012 Mac Pro. Bluetooth needs drivers (which you can extract from Apple's bootcamp drivers, or just leave it alone- the Mac Pro Bluetooth card emulates a USB HID keyboard and mouse with the devices you used to select the OS from the chooser screen if you don't install the BT chipset drivers), and the AMD Catalyst drivers should be installed for best performance- but other then that it absolutely flies, even off a USB disk drive.

    This is NOT bootcamp. Bootcamp runs through a CSM module under EFI that allows one to boot MBR-based operating systems from a legacy partition. Windows 8 x64 natively supports EFI booting from a USB flash key or USB disk drive on damned near every recent Macintosh I've tried (2012 iMac, 2012 Macbook Pro, 2010 Mac Pro) flawlessly, which has nothing to do with Bootcamp at all.

    So if you're stuck with a RAID card that only really works in OS X and you don't want to mess with that, then this is a totally viable alternative to run Windows on your Mac Pro.

    -SC
     
  2. macrumors 601

    ActionableMango

    Joined:
    Sep 21, 2010
    #2
    I don't see what's new. I've never had to use Bootcamp. AFAIK, all Bootcamp Assistant does is partition the drive and let you create bootcamp driver disc.

    I just install Windows from the DVD directly to its own HDD just like I would on any generic PC. The drivers I just get from the Internet. Works with Windows 7 x64.
     
  3. macrumors 6502a

    monkeybagel

    Joined:
    Jul 24, 2011
    Location:
    United States
    #3
    FYI - It does not work on a 2010 Mac mini. Setup gets to the point where Installing Devices and it reboots and setup restarts stating that an error occurred and that Setup needs to be re-run. This was with Windows 8 Enterprise x64. So far I haven't found a workaround, but I like Windows 8 so little I haven't put a great deal of effort into it.

    ----------

    There is in fact a difference. You know when you have a non OS X disc in the drive and hold Option to boot from the optical drive, you will always see it labeled "Windows?" If you select this, the Macintosh changes the way it presents the partition table to the OS to support/fake an MBR disc.

    When selecting EFI Boot, it does not do this and presents the disc as a GPT disc and Windows installs in EFI mode using the EFI partition and boot manager.
     
  4. macrumors 601

    ActionableMango

    Joined:
    Sep 21, 2010
    #4
    Very informative, thank you!
     
  5. thread starter macrumors 6502a

    Joined:
    Oct 4, 2008
    #5
    Actually, it doesn't.

    Bootcamp.app (the utility) simply creates a hybrid GPT/MBR partition table. Both are available to the OS running under "Bootcamp", that's how Apple's Bootcamp HFS+ drivers work (which allow you to read and write to your OS X partition). Only the MBR bit is used when booting a legacy OS though.

    The other half of Bootcamp (the bit inside your system firmware) is actually a chunk of code (called a "CSM", or Compatibility Support Module) that emulates a bog standard (and highly limited) PC BIOS complete with a VGA BIOS to drive your graphics card. This PC BIOS takes over the computer hardware after EFI has initialized the hardware and launched the CSM, and is what loads up a boot loader off an MBR-based partition table.

    Under EFI or the CSM, the operating system has the same direct access to the disk drive irregardless. There is no tomfoolery that changes how the partition table is presented to the OS, it's just that the MBR-based partition table is required by the emulated PC BIOS to boot such an operating system.

    EFI booting is totally different and more direct. There's no emulation layer of any kind. EFI loads an executable off a FAT32 partition (or HFS+ in the case of Mac OS X) and runs it, this loads and starts the OS kernel, which then can mount whatever filesystem your OS uses.

    -SC
     
  6. macrumors 6502a

    monkeybagel

    Joined:
    Jul 24, 2011
    Location:
    United States
    #6
    What causes, in some cases, for the Windows 7 installer to see all disks as GPT but a subsequent reboot to see it as MBR, and EFI boot is not selected in either instance?
     

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