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zarmanto

macrumors regular
Original poster
Feb 3, 2014
178
124
Around the corner from the 7/11
Background: I have a Late 2012 iMac which is still working perfectly; I intentionally configured it to the highest specs I could afford, for greater longevity. (27"/32GB RAM/3TB HDD/3.2GHz/NVIDIA 680MX) Those who have similar vintage hardware and who have bothered to look closely enough at Disk Utility may have noticed that the Bootcamp Assistant does some decidedly odd things on that generation of computers, whenever the hard drive is greater than 2TB. Apparently, Windows can only boot from a partition which is located entirely within the first 2TB of that drive, but Mac OS X insists on claiming the first position on the hard drive. Thus, in order to allocate all of the drive space accordingly, your drive basically ends up sliced into multiple pieces, looking something like this:

|---- MacOS partition (part 1) ----| |-- Windows partition --| |---- MacOS partition (part 2) ----|

I get that this is probably sub-optimal, and I get that newer computers with a more modern boot paradigms apparently don't suffer from this limitation. What I don't get, is why Mojave absolutely refuses to install, when your machine is partitioned according to this paradigm. And then, to compound the issue, Mojave offers the recommendation that you remove your Bootcamp partition if you still want to update, stating that your iMac will never again be able to use Bootcamp, afterwards.

I mean... just... what the -- ??

(Background TLDR: Just read the subject line.)

Potential solution: So anyway, I obviously haven't upgraded yet. I'm considering whether or not I want to try an alternate option; specifically, I'm thinking of buying an external Thunderbolt SSD, and attempting to install Mojave on that instead. In theory, I might be able to keep my existing Bootcamp on the internal drive alongside the existing High Sierra installation, as well as potentially boost my overall performance (under Mojave) with that more responsive SSD. Of course, I'm fully expecting that at a minimum I'll need to install High Sierra on the SSD first and be booting from that volume, in order to bypass the Mojave Installer's built-in Bootcamp blockade.

Has anyone else had experience with similar configurations, who might be able to provide some insights on my proposed solution/workaround?
 

mikehalloran

macrumors 68020
Oct 14, 2018
2,077
605
The Sillie Con Valley
If you want to boost performance, get rid of that HHD.

You can install a 2T SATA blade for less than $400 plus a 2T SSD for less than $300. A 4T SSD lists for $800 and can be found for less. So, right now 2+2 costs only a few $ less than a single 4T.

Because of Bootcamp and those issues, I would not make a fusion drive. There's no advantage on a 2012 anyway if both are SSDs.

The SATA blade on any 2012 Mac is unique to that year and there are no 2T system pulls. 2T SATA blades for PCs are readily available in the aftermarket as are adapters that let them work in 2012 Macs.
 

zarmanto

macrumors regular
Original poster
Feb 3, 2014
178
124
Around the corner from the 7/11
If you want to boost performance, get rid of that HHD.
I'm quite well aware of that; that's why I'm thinking about using a Thunderbolt SSD. That said: my primary concern in this venture is not specifically the performance boost, but rather, upgrading to Mojave while retaining the ability to boot into Windows via Bootcamp. I only see the potential for a performance boost as a reasonable secondary benefit of using an SSD to solve the primary concern.

You can install a 2T SATA blade...
I'm not entirely certain where you're going with this; are you suggesting that I install third-party add-ons inside my iMac? If so, I suppose I should have noted at the outset that I really have no desire to crack this Mac open, this late in its lifecycle. I'd prefer to do what I can with external add-ons, if at all possible.

Because of Bootcamp and those issues, I would not make a fusion drive. ...
That is not my intention; I was only speculating on the idea of booting directly from an external Thunderbolt SSD -- no Fusion involved, here. I think maybe we just got our signals crossed, possibly because of my comment in another thread on a peripherally related topic.
 

mikehalloran

macrumors 68020
Oct 14, 2018
2,077
605
The Sillie Con Valley
are you suggesting that I install third-party add-ons inside my iMac?

I believe that I was perfectly clear on this point.

Highlighting inside does not make it the bad thing. You have a 6 year old, slow, very hot motor inside your 2012 and cooking its guts. The average age for failure is 5 years for these.

The best thing you can do is open it up, get it out of there and put something else in that runs much, much cooler and way faster. Going external does not get that thing out of there—you can open it up and disconnect it but you might as well install an SSD once inside.

What you want to do is easy. It's not a simple clone of the old system but yes, you'll get it working eventually. If using HHDs, the only way to make it faster with the same capacity is a multi-drive assembly in a RAID array (not cheap!). Otherwise, get an external housing and throw a 4T SSD into it—this will limit you to the 6G SATA limit (same as putting it inside) but still a lot faster than what you have now.
 

zarmanto

macrumors regular
Original poster
Feb 3, 2014
178
124
Around the corner from the 7/11
I believe that I was perfectly clear on this point. ...
Not to belabor the point, but usually when someone expresses uncertainty and asks a clarifying question, the implied commentary is that they didn't think you were as clear as you thought you were. For instance, I thought that by specifically proposing a Thunderbolt drive as my potential solution, that it would be clear that I was not seeking out internal solutions. By your feedback, you presumably would not agree with that initial premise. Nonetheless, thank you for your thoughts.

Back to the original question: Does anyone else have specific experience or thoughts on the Thunderbolt option, and its viability to resolve the stated problem?
 

mikehalloran

macrumors 68020
Oct 14, 2018
2,077
605
The Sillie Con Valley
I answered your question and also gave you a better solution.

Others may have different opinions but they won't be better than mine which are based on experience.

If you are going to try to keep a 2012 going for a long time, replace that hard drive—currently, the maximum available SSD is 4T. You also have the opportunity to replace the blade up to 2T. You may tie the both together for a 6T fusion if you like but, since both are SATA III, there's neither a performance hit nor benefit to doing so. A 2T blade + 2T SSD costs about the same as a 4T SSD. That will probably change in 6 months or so.

It's your Mac, not mine. I don't care which route you take but my advice is sound.
 

zarmanto

macrumors regular
Original poster
Feb 3, 2014
178
124
Around the corner from the 7/11
Just a quick update to anyone who happens to stumble upon this old thread in search results or the like: I ended up leaving that Mac on High Sierra a bit longer than I would have liked, because the Thunderbolt bus actually died entirely not long after I posted this thread. (It's no longer my primary workstation, at this point.)

Also, in a peripherally related experiment, I recently installed a new SSD inside a 2012 Mac Mini. (A Mini is way easier to get into than an iMac.) In-so-doing, I learned a pretty important lesson: not all SSDs are inherently cooler than their older HDD counterparts; that Mini now needs a literal ice-pack resting on top of it, in order to watch certain streaming video content without heating up to the point that the CPU chokes. I'm still trying to decide on exactly what my next step needs to be, to remedy this new issue... but at the very least, it'll certainly require swapping that overly hot SSD out for something else.

Realistically, no amount of research was likely to reveal this potential issue, since pretty much everybody online seems to be of the same opinion as Mike, in regards to SSDs supposedly running cooler than HDDs... so I thought I'd chronicle my experiences here, in case someone else ends up experiencing similar issues.

I guess the moral of the story is this: Never assume that anything you read online (or anywhere else, for that matter) is absolute truth, even if nearly everyone is saying it.
 
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