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Just installed Bootcamp on a late 2013 iMac 27". It was running a fully updated Mojave OS before running Bootcamp Assistant. Installed Windows 10 image from Microsoft download. After installing Windows all worked fine and did all its updates. But now, none of the Mac startup keyboard commands work. I can't launch startup manager or recovery mode. It just goes straight to Windows. If I use the Bootcamp windows control panel to choose start up only Windows appears in the list. If I choose Advanced Startup Options in Windows I choose a USB or drive but it just boots straight back into Windows 10.

I've tried every shortcut on this page (on a USB keyboard) https://support.apple.com/en-us/HT201255

Even the PRAM reset shortcuts don't work. Is it the UEFI? How do I reset this?

Any ideas?

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  • Do you have set an EFI-Password ?
    – bot47
    Aug 7, 2019 at 10:50
  • No, no EFI password was set
    – Luke H
    Aug 9, 2019 at 1:31

2 Answers 2

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It sounds like you updated the firmware on the video card. The drive selection screen and other startup keystrokes work from the original EFI. This likely happened when updating W10. You may have accidentally also updated a video driver that included a VC firmware update. Been there, done that. Getting the card re-flashed to the Apple VC EFI is likely to be difficult and/or expensive. This is especially true since this is an iMac. The video card is integrated into the logic board. My solution won't work for you, unfortunately.

Perhaps an Authorized Service Provider can flash it. If you're not sure where to go, try Apple first. Call (800-275-2273) or go to the support site and when you get through all the repair prompts, it will show a map of the services near you. Perhaps the Genius Bar can flash it, too. Don't let 2013 deter you from calling. They may be able to help on the phone (doubt it), but they can at least help you find a place to get it done.

If you have not been able to start the Mac OS, as a Hail Mary, try holding 'x' during startup to see if you can get the MacOS to start (which you may have already). Or use Target Disk Mode to remove the Windows partition. When the Mac can't find an OS on the selected startup disk, it looks for a new one and it may startup from the Mac OS. Then you can use Sys Prefs to change your startup disk back to the Mac OS.

However, if you no longer have a Mac OS (deleted partition maybe?), then it will start in Internet Recovery. If you have a Time Machine backup, you can restore the your original Mac OS and content using your backup. Otherwise, you will have to reinstall the OS.

Let me say this. My experience with the issue (update Windows, flash card, no startup keystrokes) does not fit your scenario exactly so I could be totally wrong. If you don't have a backup and have data to retrieve, try Target Disk Mode before making any changes. You can save important data (assuming it still on the hard drive) to an external hard drive.

Good luck.

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  • The partitions are both there. It's just the ability to boot into OS X is removed. Event the BootCamps control panel in Windows couldn't see Mac partition. If I use Windows advanced startup I select USB or CS and I see OS X there but when I click restart it just goes straight back to Windows. I took it to Apple who said they can't flash the EFI and it needs a new motherboard. Never using Bootcamp again
    – Luke H
    Aug 9, 2019 at 1:33
  • Boot camp wasn't the issue. It was the update. I would still try the 3rd party root. Google search "Mac repair." Let Google detect your location to get a map of service providers. They may not be able to do anything, but it's worth a try. Another option might be to copy the Windows partition (use a drive cloning app) to an external drive. Then remove the Windows partition from the internal drive. To use Windows, plug in the external drive and start. To use Mac OS, unplug the drive and start. Without another OS to pick at start up, it should default to the remaining OS: Mac OS.
    – D. Geren
    Aug 10, 2019 at 1:57
  • One final solution. You might find a good deal on a newer iMac 27" on ebay. Then you can use your current machine for Windows and the new one for the Mac OS. Install a mouse sharing app (like MouseShare) to allow one keyboard and mouse to control both computers; just move the mouse from one screen to the other and the keyboard switches, too. Or you can get a USB switch from Amazon or Best Buy. With a push of a button, you change which computer is operated by the keyboard and mouse (like a KVM, but with the Video part). You can also plug a USB printer into it for use on both machines.
    – D. Geren
    Aug 10, 2019 at 2:01
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I had the same issue. Using bluetooth or wireless keyboard was the problem in my case. Rebooting from Bootcamp to Mac was too fast for the bluetooth/wireless keyboard connection. Switching to a cable connection fixed the issue.

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