GUIDE: How to get back old EFI after downgrade from Yosemite

Discussion in 'OS X Yosemite (10.10)' started by ewbte, Oct 18, 2014.

  1. ewbte, Oct 18, 2014
    Last edited: Nov 27, 2014

    ewbte macrumors newbie

    Oct 1, 2014
    Yosemite also updates your EFI on install, so when you downgrade to previous version of OS X, you still have new "awesome" design in startup manager.

    1. You need to download EFI for your mac (until they didn't update the page).
    2. Be sure you downloaded right EFI, otherwise it could end up bad!
    3. Get unpkg
    4. Use unpkg on *.pkg with your EFI, then copy the folder you got to /Applications/Utilities/
    5. Open copied folder, find a .scap file.
    6. Open terminal, copy there sudo bless -mount / -firmware then press spacebar.
    7. Drag .scap file to terminal.
    8. Press spacebar and copy --recovery --verbose in terminal.
    9. Press enter, type password and press enter again.
    10. Shut down your mac from menu, wait until it will turn off.
    11. Wait a bit, then turn on your computer but do NOT hold the power button down. The screen will turn black and remain in that state for up to 40 seconds. A gray screen will appear and a status bar indicates the progress of the update.

    i.e. for 13-inch rMBP late 2012 I did this:
    Notice that terminal dont recognise spacebars in path, add a \ before space between words, like in example I provided.

    Do it on your own risk!

    Hope you did everything right and enjoy your awesome OS X as nothing happened c:
  2. bravobohan macrumors newbie

    Oct 17, 2014
    No one has mention this before. Thanks. One question is downgrade EFI a must?
  3. ewbte thread starter macrumors newbie

    Oct 1, 2014
    No it is not, just in case you don't like black startup manager with newish icons.
  4. knmdk macrumors newbie

    Dec 12, 2012
    Is there anyone who was lucky enough to downgrade EFI Boot ROM firmware on 15-inch MacBook Pro with Retina display (rMBP)?

    Here’s my story.

    I’m running OS X 10.9.5 (13F1112) (Mavericks) on 15-inch rMBP (Mid 2012, MacBookPro10,1). I never did update to OS X 10.10 or 10.11. However I’ve installed Mac EFI Security Update 2015-001 as it’s description didn’t say about new EFI Boot ROM UI. So now I have that black screen, new icons and fonts in my boot menu (Yosemite or El Capitan style). And since I use boot menu often I feel inconsistency of my laptop. Another issue i my rMBP fans are full speed with the tiny system usage in Windows 7 (a couple of light tabs in Google Chrome and it starts rolling).

    I’ve decided to downgrade Boot ROM from MBP101.00EE.B09 (as my System Information and Apple Support article says) to MBP101.00EE.B02 (as this archived Apple Support article says). So I downloaded MacBook Pro Retina EFI Update 1.0 and extracted MBP101_00EE_B02_LOCKED.scap from DMG/PKG using unpkg.

    As guides tell (here and here), I did run
    sudo bless -mount / -firmware <SCAPFileLocation> --recovery --verbose
    Terminal replied everything’s fine (no errors or permission issues). I then shut rMBP down and turned it back on. All it did was 4-5 silent noises and then a normal boot to OS X (however with a bit long loading indicator on the first grey screen). So no EFI Boot ROM firmware being updated indication on grey screen. I did double-check and run
    sudo bless -mount / -firmware <SCAPFileLocation> --recovery --setBoot --nextonly --verbose
    clear ; diskutil mount /dev/disk0s1 ; ls -l /Volumes/EFI/EFI/APPLE/FIRMWARE/ ; diskutil unmount /dev/disk0s1
    So in the output I saw the MBP101_00EE_B02_LOCKED.scap file was located on disk0s1 (EFI).

    I did a couple of tries more with the same result: 4-5 silent noises and then a normal boot to OS X (takes a while longer than usually).Boot ROM version still same - MBP101.00EE.B09. I then run
    sudo diskutil mount /dev/disk0s1 ; sudo rm /Volumes/EFI/EFI/APPLE/FIRMWARE/MBP101_00EE_B02_LOCKED.scap ; sudo diskutil unmount /dev/disk0s1
    I did SMC as Apple Support article says and now there’s no delay on first grey screen.

    Since this guide clearly states EFI Boot ROM firmware can be downgraded on 13-inch rMBP may someone point me what am I doing wrong to downgrade on 15-inch rMBP? I did a little research on bless command at Mac Developer Library and it seems my command syntax is all good.
  5. chrfr macrumors 604

    Jul 11, 2009
    You should understand that trying to do this is a terrible idea.
    You could leave your computer unusable, and you open up the computer to security vulnerabilities. Is it worthwhile to do this for something you see for at most 30 seconds a day? My computers go weeks between reboots, so I cannot understand why you'd care so much about a boot screen.
  6. grahamperrin macrumors 601


    Jun 8, 2007
    The downgrade was not for booting alone. If I understand correctly, it was also for:

    Cross reference: Did Yosemite Update Boot Firmware?
  7. chrfr macrumors 604

    Jul 11, 2009
    The EFI update isn't causing the fans to run fast in Windows. It's CPU load from something else. (...and no, I'm not digging down the rabbit hole of the other thread you're linking here without context.)
  8. knmdk macrumors newbie

    Dec 12, 2012
    Yes I've been experiencing unusual behavior of fans in my rMBP after that Mac EFI Security Update 2015-001. After further attempts I never succeeded downgrading and finally decided to do a clean installation of OS X El Capitan. I'm quite happy with it and laptop feels solid again. However the fans problem when running Boot Camp didn't go away. So I give up for now.
  9. ramzimehana macrumors newbie

    Apr 18, 2016
    Great guide here, however the file I am extracting isn't giving me the same files as you have mentioned here.

    Any help would be great, this issue is driving me mad and I have been experiencing it for a few months now, with no work around.
  10. ewbte thread starter macrumors newbie

    Oct 1, 2014
    Hm, I have no idea what you have there. I've done it a couple of times with my mbpr late2012 and mba mid2012, both worked the same way for me.

Share This Page