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

ewbte

macrumors newbie
Original poster
Oct 1, 2014
6
1
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 http://support.apple.com/kb/ht1237 (until they didn't update the page).
2. Be sure you downloaded right EFI, otherwise it could end up bad!
3. Get unpkg http://www.timdoug.com/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:
sudo bless -mount / -firmware /Applications/Utilities/MacBookProRetinaEFIUpdate/System/Library/CoreServices/Firmware\ Updates/MBPRetinaEFIUpdate-1.1/MBP102_0106_B03_LOCKED.scap --recovery --verbose
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:
 
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ewbte

macrumors newbie
Original poster
Oct 1, 2014
6
1
No it is not, just in case you don't like black startup manager with newish icons.
 

knmdk

macrumors newbie
Dec 12, 2012
5
1
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
Code:
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
Code:
sudo bless -mount / -firmware <SCAPFileLocation> --recovery --setBoot --nextonly --verbose
then
Code:
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
Code:
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.
 
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chrfr

macrumors G3
Jul 11, 2009
8,206
2,530
Is there anyone who was lucky enough to downgrade EFI Boot ROM firmware on 15-inch MacBook Pro with Retina display (rMBP)?
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.
 
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chrfr

macrumors G3
Jul 11, 2009
8,206
2,530
The downgrade was not for booting alone.
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.)
 

knmdk

macrumors newbie
Dec 12, 2012
5
1
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.
 

ramzimehana

macrumors newbie
Apr 18, 2016
1
0
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.
 

ewbte

macrumors newbie
Original poster
Oct 1, 2014
6
1
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.
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.
 

ScunnerDarkly

macrumors newbie
Dec 15, 2017
5
11
UK
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.
This thread may be 10+ years old but it is still a relevant question.

Reverting firmware isn't a terrible idea if there is a specific need for performing it. Yes, there are associated risks but chances are someone wanting to go down this route will be technically competent enough to understand the hazards.