[NEWS] macOS Mojave Boot Camp issues on 2012 27" iMac

[Your Name]

Do NOT upgrade to Mojave if you use a 2012 27" iMac and need to use
Windows via Boot Camp.

From MacRumors.com ...

Boot Camp Won't Work With macOS Mojave on 2012 27" iMac With 3TB Hard Drive
---------------------------------------------------------------------------
Apple today shared a support document that will be of interest to customers
who own a late 2012 27-inch iMac with a 3TB hard drive and are attempting
to upgrade to the macOS Mojave update.

There is an issue on this iMac model that results in the following alert
when attempting to install macOS Mojave: "Installation cannot proceed with
Boot Camp configured."

To fix this problem, Apple says that customers with the 2012 27-inch iMac
with 3TB hard drive will need to completely remove the Boot Camp partition
using Boot Camp Assistant before macOS Mojave can be installed.

After upgrading to macOS Mojave, Boot Camp will not be able to be used to
install Windows on these machines. No other iMac models appear to be
affected by this issue.

<https://www.macrumors.com/2018/09/24/no-boot-camp-2012-3tb-imac-mojave/>

[Alan Browne]

On 2018-09-24 16:53, Your Name wrote:
>
> Do NOT upgrade to Mojave if you use a 2012 27" iMac and need to use
> Windows via Boot Camp.
>

<S>

>   To fix this problem, Apple says that customers with the 2012 27-inch
> iMac
>   with 3TB hard drive will need to completely remove the Boot Camp
> partition
>   using Boot Camp Assistant before macOS Mojave can be installed.
>
>   After upgrading to macOS Mojave, Boot Camp will not be able to be
> used to
>   install Windows on these machines. No other iMac models appear to be
>   affected by this issue.

That's a bizarre bug. This iMac is the late 2012 / 27 inch version -
but 1 TB fusion drive.

IAC I've never even tried bootcamp. VMWare Fusion is a better solution
for me.

--
"2/3 of Donald Trump's wives were immigrants. Proof that we
need immigrants to do jobs that most Americans wouldn't do."
- unknown protester

[JF Mezei]

On 2018-09-24 17:19, Alan Browne wrote:

> That's a bizarre bug. This iMac is the late 2012 / 27 inch version -
> but 1 TB fusion drive.

Is Mojave the first version that supports/converts Fusion system drives
to APFS? Could this be the glitch?

Just curious on what is different on that specific model ?

Also, when booting Windows on a machine with Fusion drives, did Apple
provide special Windows disk drivers to handle Fusion drives?

When moving to APFS, isn't there the problem of OS-X deciding to take
over all of the SSD and shove everything else to the hard drive, which
would meen putting the WIndows boot blocks out of reach of EFI which
expect it on the SSD?

[Alan Browne]

On 2018-09-24 19:00, JF Mezei wrote:
> On 2018-09-24 17:19, Alan Browne wrote:
>
>> That's a bizarre bug. This iMac is the late 2012 / 27 inch version -
>> but 1 TB fusion drive.
>
> Is Mojave the first version that supports/converts Fusion system drives
> to APFS? Could this be the glitch?
>
> Just curious on what is different on that specific model ?
>
> Also, when booting Windows on a machine with Fusion drives, did Apple
> provide special Windows disk drivers to handle Fusion drives?

I suspect that Bootcamp Windows was benefiting from fusion.

>
> When moving to APFS, isn't there the problem of OS-X deciding to take
> over all of the SSD and shove everything else to the hard drive, which
> would meen putting the WIndows boot blocks out of reach of EFI which
> expect it on the SSD?

The bug is specific to 3TB drives in that model year only - for some
undeclared reason. Not SSD's, not 1 TB fusion drives, not ordinary drives.

[Malcolm]

It's probable because Windows needs different drivers and partition map
for drives bigger than 2.2 TB. Above 2,2 TB, 32 bits is not enough to
address all the disk blocks,

<https://support.microsoft.com/en-us/help/2581408/windows-support-for-hard-disks-that-are-larger-than-2-tb>

[Your Name]

Nope. Boot Camp was already working with these 3TB drives - the article
mentions that people may already be using it before they upgrade. The
problem is something to do specifically with Mojave and these 2012 27"
iMacs in particular.

[Lewis]

In message <ZrudnYH5DuV3yTTG...@giganews.com> Alan Browne <bitb...@blackhole.com> wrote:
> On 2018-09-24 16:53, Your Name wrote:
>>
>> Do NOT upgrade to Mojave if you use a 2012 27" iMac and need to use
>> Windows via Boot Camp.
>>
> <S>

>>   To fix this problem, Apple says that customers with the 2012 27-inch
>> iMac
>>   with 3TB hard drive will need to completely remove the Boot Camp
>> partition
>>   using Boot Camp Assistant before macOS Mojave can be installed.
>>
>>   After upgrading to macOS Mojave, Boot Camp will not be able to be
>> used to
>>   install Windows on these machines. No other iMac models appear to be
>>   affected by this issue.

> That's a bizarre bug. This iMac is the late 2012 / 27 inch version -
> but 1 TB fusion drive.

> IAC I've never even tried bootcamp. VMWare Fusion is a better solution
> for me.

I have run Boot Camp once or twice in the past, but anymore it really
does seem pointless. VMWAre and Parallels and VirtualBox are all much
better solutions for running Windows.

I mean, VirtualBox used to be pretty terrible, and now it's pretty good.

But honestly, the only thing I've used in several years for the rare
times I need to run some "windows" utility is wine.

--
Once upon a time, a woman was picking up firewood. She came upon a
poisonous snake frozen in the snow. She took the snake home and nurse it
back to health. One day the snake bit her on the cheek. As she lay
dying, she asked the snake, "Why have you done this to me?" And the
snake answered, "Look, bitch, you knew I was a snake."

[Lewis]

In message <xZWdnUeqiecF8DTG...@giganews.com> Alan Browne <bitb...@blackhole.com> wrote:
> On 2018-09-24 19:00, JF Mezei wrote:
>> On 2018-09-24 17:19, Alan Browne wrote:
>>
>>> That's a bizarre bug. This iMac is the late 2012 / 27 inch version -
>>> but 1 TB fusion drive.
>>
>> Is Mojave the first version that supports/converts Fusion system drives
>> to APFS? Could this be the glitch?
>>
>> Just curious on what is different on that specific model ?
>>
>> Also, when booting Windows on a machine with Fusion drives, did Apple
>> provide special Windows disk drivers to handle Fusion drives?

> I suspect that Bootcamp Windows was benefiting from fusion.

>>
>> When moving to APFS, isn't there the problem of OS-X deciding to take
>> over all of the SSD and shove everything else to the hard drive, which
>> would meen putting the WIndows boot blocks out of reach of EFI which
>> expect it on the SSD?

> The bug is specific to 3TB drives in that model year only - for some
> undeclared reason. Not SSD's, not 1 TB fusion drives, not ordinary drives.

Having a 2012 iMac with 3TB fusion drive I did have problems with the
fusion drive. Apple had to replace it, and then I decided Fusion was
stupid and replaced the SSD with a 1TB SSD and 'broke' the fusion Drive,
so I have a 1TB boot drive and a 3TB data drive.

--
Friction can be a real drag.

[David Empson]

JF Mezei <jfmezei...@vaxination.ca> wrote:

> On 2018-09-24 17:19, Alan Browne wrote:
>
> > That's a bizarre bug. This iMac is the late 2012 / 27 inch version -
> > but 1 TB fusion drive.
>
> Is Mojave the first version that supports/converts Fusion system drives
> to APFS? Could this be the glitch?

The support article is talking about an iMac model with a hard drive,
not a Fusion drive (it might have been badly worded and actually cover
both hard drives and Fusion drives).

When you install Mojave, APFS conversion is done for all destination
drive types (SSD, Fusion, hard drive), so the issue is probably related
to APFS.

> Just curious on what is different on that specific model ?

Boot Camp on a 3 TB Fusion drive required a complex arrangement with the
Windows partition starting within the first 2 TB of the hard drive (for
BIOS compatibility reasons). The Core Storage container was split around
the Windows partition.

I haven't seen details for how Boot Camp was set up on an iMac with a 3
TB hard drive but it probably requires the same arrangement, forcing the
use of Core Storage spanning two partitions on the hard drive even if
the Mac side wasn't using FileVault.

Perhaps that arrangement was only used on the Late 2012 iMac, which was
the first Mac supplied by Apple with a drive larger than 2 TB? Later
models may have had firmware changes which relaxed the 2 TB limit for
Windows, allowing Boot Camp to be in a partition at the end of the hard
drive and the Mac to have a contiguous range of blocks for Core Storage
or APFS.

Perhaps APFS does not support splitting a container between two
partitions on the same drive, whereas Core Storage does support that?

> Also, when booting Windows on a machine with Fusion drives, did Apple
> provide special Windows disk drivers to handle Fusion drives?

No.

The Windows partition is in a normal GUID partition on the hard drive.
It doesn't involve the SSD at all.

The Mac Fusion drive is a group of Core Storage containers which cover
the SSD (in one GUID partition) and the rest of the hard drive (in one
or two GUID partitions, depending on Mac model, hard drive size and
whether Boot Camp is enabled).

Windows ignores the Core Storage partitions.

> When moving to APFS, isn't there the problem of OS-X deciding to take
> over all of the SSD and shove everything else to the hard drive, which
> would meen putting the WIndows boot blocks out of reach of EFI which
> expect it on the SSD?

No.

--
David Empson
dem...@actrix.gen.nz