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EFI Modifications Leaves iMac Unbootable?
jerbare writes "In attempting to run Linux and Windows on the new iMac Core Duo, people experimenting with configuring the EFI Console/Boot loader have found they can no longer boot the machine at all. Dave Schroeder of appleintelfaq.com comments, 'We have already irreversibly lost a couple of iMacs trying to load various EFI modules'. Instructions for breaking the iMac's are presently located at the bottom of the comments."
When the iMac is in this broken state, it doesn't boot, chime, show anything on the screen, or read from media.
;-)
Can't exactly "reinstall from the 10.4.4 media".
Zapping NVRAM (still supported with cmd-opt-P-R), removing the motherboard battery and letting it sit with AC for an extended period, and disconnecting the hard drive all do not revive the machine.
Hello. Just to give a bit of an update on this issue...
The iMacs in question were rendered unbootable by trying to load additional modules from Intel's EFI Sample Implementation. It is not known which module is at fault currently.
Once the iMac is unbootable, it doesn't chime, boot, attempt to access media, or display an image on the screen. Attempts to zap NVRAM (cmd-opt-P-R is still supported for this task on Intel-based Macs), remove the motherboard battery and leave the AC power disconnected for an extended period of time, and disconnecting the hard disk do not resolve the issue.
At present, we seem to have a number of difficult situations that prevent the installation of Windows directly on Intel-based Macs:
1. Apple did not include its own EFI shell or other tools to access the EFI with the Intel-based Macs, so the tools used have consisted of Intel's EFI Sample Implementation, and Tianocore's EFI Developer Kit.
2. Apple's EFI implementation does not include CSM (Compatibility Support Module), the BIOS backward compatibility layer necessary for booting 32-bit versions of Windows (pre-Vista), such as Windows XP.
3. 32-bit versions of Windows do not currently support booting an EFI machine. (And the Gateway Media Center machine with EFI people keep talking about boots Windows XP Media Center Edition 2005 in BIOS compatibility mode, not with EFI.)
4. Windows XP 64-bit and Windows Server 2003 64-bit support EFI, but the Intel Core Duo is a 32-bit architecture.
5. Windows Vista does support EFI, but the EFI booter (cdboot.efi) currently does not appear to be functioning, and/or it is looking for, and not finding, information that it is looking for on the installation DVD. It does display the typical Windows "Please press any key to boot from the CD..." message. However, the DVD does not appear to contain the necessary EFI boot partition, and EFI does not support UDF volumes and El Torito booting. (Yes, this is a DVD obtained via official channels.)
6. Mac OS X's startup disk control panel presents a Windows Vista installation on a FAT/FAT32 volume as a valid bootable volume, but Windows Vista does not support booting from a FAT/FAT32 partition, only NTFS. Mac OS X can read NTFS volumes, but not write to them. This is currently the stage we're at now. No, I haven't tried "just hooking up a drive with Vista installed" (as many have asked elsewhere) or forcibly creating an NTFS partition whose contents are an already-installed instance of Vista.
7. grub, elilo, etc., all do not work on the Intel-based Macs at this time.
Eventually, whatever method boots Windows natively will have to have a nice wrapper put around it to make it easy for a normal person to do so, and easily dual boot in addition.
To regurgitate what I've said a bit elsewhere, the real benefit to most people will come from running Windows alongside Mac OS X in a "virtual machine" environment, in a window or even full screen, with, for example, a hotkey to switch back and forth between Mac OS X and Windows. To many users who prefer Mac OS X, particularly in enterprise, academic, and research environments, but who also have the occasional applications (usually administrative) that require Windows, this configuration would be a holy grail of sorts. And in this configuration, Windows wouldn't be running in emulation, but it would be running at essentially the native speed of the underlying hardware (with the exception of graphics and disk I/O performance). It will be *much* faster than any emulation ever has been, and there will no doubt be several open source (qemu, xen, wine) and commercial (vmware, Virtual PC) that will allow running Windows (or Windows software) in various capacities. Intel's Virtualization Technology (VT), allowing multiple operating systems to run in separate hardware "partitions" on one
From Dave Schroeder posted 01/23/06
By following these steps, the iMacs that had difficulty with certain EFI modules appear to have been restored to a functioning state:
- Disconnect the internal hard disk
- Disconnect the iMac from AC power
- Plug in AC while holding the power button
- Power up the iMac and zap NVRAM (cmd-opt-P-R)
The hard disk can be reformatted and the operating system restored.