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Small warning for those wanting to 'try' Yosemite

kwokaaron

kwokaaron

macrumors 6502a
Original poster
Sep 20, 2013
574
257
London, UK
Although downgrading works if you don't like Yosemite, bear in mind that all new macs (all Haswell-based Macs, and Ivy Bridge rMBP 15" and 13") also get their EFI/SMC firmware upgraded as well. So downgrading back to Mavericks will make the startup screen when it chimes and the drive selection screen black instead of the white/grey...

Edit: When I meant new, I meant 2012 onwards
 
Last edited:
fisherking

fisherking

macrumors G4
Jul 16, 2010
11,090
5,440
ny somewhere
kwokaaron said:
Although downgrading works if you don't like Yosemite, bear in mind that all new macs (all Haswell-based Macs, and Ivy Bridge rMBP 15" and 13") also get their EFI/SMC firmware upgraded as well. So downgrading back to Mavericks will make the startup screen when it chimes and the drive selection screen black instead of the white/grey...
Click to expand...

and the point is? the OS that comes with a new mac is the 'oldest' OS you should run on that mac. as is always the case...
 
chrfr

chrfr

macrumors G5
Jul 11, 2009
13,520
7,047
fisherking said:
and the point is? the OS that comes with a new mac is the 'oldest' OS you should run on that mac. as is always the case...
Click to expand...

The firmware update and black screen change applies at least to 2013 computers, which shipped with Mavericks.
 
kwokaaron

kwokaaron

macrumors 6502a
Original poster
Sep 20, 2013
574
257
London, UK
chrfr said:
The firmware update and black screen change applies at least to 2013 computers, which shipped with Mavericks.
Click to expand...

The earliest Mac (Ivy Bridge rMBP) that support this firmware change came with Lion. ;)

fisherking said:
and the point is? the OS that comes with a new mac is the 'oldest' OS you should run on that mac. as is always the case...
Click to expand...

What I meant was Macs that are comparatively new which doesn't have Yosemite preinstalled will have their firmware upgraded as part of the OS. While this isn't such a big deal itself, those that might downgrade it back to a previous OS will find the startup sequence inconsistent since the selection screen has changed into black while the loading of the OS (pre-yosemite) itself is grey.
 
chrfr

chrfr

macrumors G5
Jul 11, 2009
13,520
7,047
kwokaaron said:
The earliest Mac (Ivy Bridge rMBP) that support this firmware change came with Lion. ;)
Click to expand...

I don't have access one of those, but the 2012 11" Air I have did not get a firmware update with Yosemite, hence the "at least" in my response.
 
M

Manic Harmonic

macrumors 6502
Dec 4, 2011
299
1
If you reboot twice after downgrading to Mavericks it should revert to white. It's not the firmware that changes the color, it's boot.efi. The boot.efi hack for the black boot screen on unsupported Macs changes the boot menu to black as well... The first time booting back into Mavericks, it's just a black screen, but after rebooting a few times it's white again. Then if you boot Yosemite again it takes a few reboots to return to black.
 
kwokaaron

kwokaaron

macrumors 6502a
Original poster
Sep 20, 2013
574
257
London, UK
Manic Harmonic said:
If you reboot twice after downgrading to Mavericks it should revert to white. It's not the firmware that changes the color, it's boot.efi. The boot.efi hack for the black boot screen on unsupported Macs changes the boot menu to black as well... The first time booting back into Mavericks, it's just a black screen, but after rebooting a few times it's white again. Then if you boot Yosemite again it takes a few reboots to return to black.
Click to expand...

That's interesting, didn't know that. Thought it was the firmware that was messing it around. However, some users have mentioned that their macs seem to be 'stuck' on the black screen even after downgrading.

References:
https://forums.macrumors.com/threads/1818849/
https://forums.macrumors.com/threads/1745984/ (second last post)
http://apple.stackexchange.com/ques...tartup-manager-after-downgrading-to-mavericks
 
E

Ethosik

Contributor
Oct 21, 2009
7,813
6,715
thejadedmonkey said:
Have you looked at it?
Click to expand...

I remember when people downgraded from Vista, and even 7 JUST because of the looks. I cannot go back to Mavericks now, it looks so old.

The new look is much better. And does that mean you will never upgrade? Because the new look is probably here to stay for YEARS.
 
thejadedmonkey

thejadedmonkey

macrumors G3
May 28, 2005
9,184
3,345
Pennsylvania
xWhiplash said:
I remember when people downgraded from Vista, and even 7 JUST because of the looks. I cannot go back to Mavericks now, it looks so old.

The new look is much better. And does that mean you will never upgrade? Because the new look is probably here to stay for YEARS.
Click to expand...

I do (maybe) mean just that. Yosemite just doesn't cooperate with my eyes, and given the amount of system and app instability from Apple lately, I'm thinking an ultrabook with Windows 10 on it is probably the better choice. Of course, if I like the "all new redesigned 2015 macbook air", I'll probably get and install Windows 10 on that, if Windows runs alright on it.

It all depends on what happens this May(ish).
 
Traverse

Traverse

macrumors 604
Mar 11, 2013
7,688
4,400
Here
Yeah, I mentioned that in my thread.

Kind of annoying, but I'll live with it. I just wonder if it could cause issues for users running Mavericks.

----------
Manic Harmonic said:
If you reboot twice after downgrading to Mavericks it should revert to white. It's not the firmware that changes the color, it's boot.efi. The boot.efi hack for the black boot screen on unsupported Macs changes the boot menu to black as well... The first time booting back into Mavericks, it's just a black screen, but after rebooting a few times it's white again. Then if you boot Yosemite again it takes a few reboots to return to black.
Click to expand...

That was not the case with me. I have FV enabled if that changes anything.
 
grahamperrin

grahamperrin

macrumors 601
Jun 8, 2007
4,942
648
FileVault 2, Recovery OS, the recovery slice and versions of Mac OS X

Traverse said:
… FV enabled if that changes anything.
Click to expand...

Earlier:

Traverse said:
I used a 10.9.5 USB. …
Click to expand...

I wasn't sure exactly what was meant by that.

Consider that with FileVault 2, the early boot process for OS X uses the recovery slice (partition) to present users with the option to unlock the OS X slice.

Here for example:

Code: 
sh-3.2$ diskutil list disk0 | grep Apple_Boot
   3:                 Apple_Boot Boot OS X               134.2 MB   disk0s3
   5:                 Apple_Boot Recovery HD             650.0 MB   disk0s5
sh-3.2$ diskutil mount readOnly /dev/disk0s5
Volume Recovery HD on /dev/disk0s5 mounted
sh-3.2$ defaults read /Volumes/Recovery\ HD/com.apple.recovery.boot/SystemVersion
{
    ProductBuildVersion = 13F34;
    ProductCopyright = "1983-2014 Apple Inc.";
    ProductName = "Mac OS X";
    ProductUserVisibleVersion = "10.9.5";
    ProductVersion = "10.9.5";
}
sh-3.2$ diskutil unmount /dev/disk0s5
Volume Recovery HD on disk0s5 unmounted
sh-3.2$

In my case that's slice 5 of disk 0 (zero). Your Recovery OS may have a different slice number.

Essentially: check whether your Recovery OS is at Mac OS X 10.9.5. If not, it'll be timely to use Apple's full installer for that version of OS X.

Kernel Programming Guide: The Early Boot Process
 
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