Model A1419 / EMC 2806 & EMC 2834/ Late 2014 or Early 2015 or late 2015 / 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 Processor / Retina 5K display

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Fusion & Flash Storage

I am not asking about performance. I'm not asking about how any software works. I am asking about the physical components installed in the iMac 27" w/5K Retina display.

Some say Apple's machines are not designed to be opened. They are not designed to be upgraded. That is not the topic. If something is cost effective is not the topic. If something is time consuming or hard is not the topic.

This is a hardware site, other sites do reviews and software Q&A.

If I order a Fusion Drive for a iMac 27" with 5K display, I can get a 1TB HDD and 128GB of solid state flash storage. AKA the meaning of Fusion via it's marketing words.

If I order the non-Fusion Drive, I can pick the storage capacity I want, but for this case, I pick 256GB of solid state flash storage.

So now there are 2 storage options (fusion or flash) to compare which comprise 3 different physical pieces; 1TB, 128GB, and 256GB.

I'm not asking about speed, performance or capacity, or which is better or worse. I am not asking about the spinning hard disk.

The 128GB of solid state flash storage connects to the logic board (obviously), so does the 256GB.

Question #1:

is the only difference between the 128GB of flash storage (available via "Fusion" configuration from Apple)

and the

256GB Flash Storage, the fact that the capacity of 256 is twice 128?

I am asking about how the flash storage connects to the logic board. I am asking about what chip sets are used to make up the final capacity (128 or 256).

As seen here:


For above, in Fusion configuration, the memory chip is SanDisk 05131 016G 16 GB NAND Flash (8 x 16 GB = 128 GB total)

Question 2:

Maybe not a SanDisk chip, but the specs, connection, etc. are they the same between fusion solid flash storage and non-fusion solid flash storage, both PCIe blade?

True or False (question 3)

Situation 1:

A - Order Fusion Drive iMac 27" with 5K display

B - Remove spinning hard disk drive

Situation 2:

Order 27" w/5K with 256GB Flash storage option

does above situation 1 minus 128GB = situation 2? Am I missing something with this?

True or False (question 4)

If I order 27" iMac w/5K and get the 256GB Flash Storage option, there is no physical mount or retention device included in the machine to allow for a standard hard disk to be installed?

True or False (question 5)

If I order 27" iMac w/5K and get the 256GB Flash Storage option, there is no SATA connector available on the logic board to connect a SATA storage device later?

True or False (question 6)

The logic board is unique based on the the flash storage option? (I don't think this is true, but some have said the flash storage is soldered). So this is really 2 questions...

True or False (question 7)

For either Fusion or non-Fusion the solid state flash storage connects to the logic board using an Apple proprietary connection and not a mSATA?

True or False (question 8)

Order a 5K iMac with Fusion option.

(assuming removable)

Remove internal rotational HDD.

Remove internal 128GB solid storage.

Install of 3rd party SSD not possible without some retention device?

True or False (question 9)

Order a 5K iMac with 256 flash storage

Flash storage fails within warranty

Return for repair

Repair =

unplug broken 256GB apple proprietary PCIe blade

then plug-in new 256GB blade

Could a 512GB/1TB blade be installed rather than the original 256GB? (of course apple does what they do, but what would make sense based on the machine's internals)

I know many people are talking about the design and the 5K. I know people are not talking about RAM because it can be upgraded at will. Because the processor isn't fixed to the logic board, there's not much conversation there.

No one is really talking about storage. Why? Is Cloud storage what's needed? Is thunderbolt so fast that nobody cares how much internal space in within the machine?

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Greg, Boy what a list of Q's! How about cutting it down a bit here (how about 5 q's). Focus on the main points simple and straight on what you're objective is.


Also did you review the iMac teardown? Review this: iMac Intel 27" Retina 5K Display Teardown I think some of your questions can be answered there.


Dan - yup a crazy list of questions.

The main point I want to understand is if the solid storage (non-fusion) is the apple proprietary connector and what the difference is between model configs for the solid storage. If I buy a 256 non-fusion config and a 1TB non-fusion "flash storage" stick is in my possession, can the 256 be replaced with the 1TB?

If there is no real different between the solid storage of the fusion and non-fusion options, the fusion could be "broken" having 2 independent disks. And later when larger "blade/sticks" are available 128 could be changed. The only reason to order a non-fusion option is because a capacity larger than 128GB is wanted.

It seems to me the original iFix tear down doesn't investigate the difference between fusion & non-fusion machines. But that's not a criticism, I understand that nobody has seen the insides of these machines.

The 404 broken link had quotes sorry. Blog tear down - linked here:


The teardown is just that a breakdown of the unit. It does not get into the details of how the systems storage can be configured.


Sounds to me like you expect to customize the family car (iMac) attempting to turn it into a pickup or dump truck with after market beds. . . not feasible. There are three on-board storage connectors, two are SATA one is proprietary. As Dan explains below (at this time) only Proprietary Blade drives fit this connector. Its possible that in the future someone may make an adapter or find a source for larger blade drives Are there larger blade drives, and where and when will these drives become available are imponderable questions. Looking to the future with more and more storage desirable on an iMac, and even the MacPro external drives are the soluiton... which may also be "fusion" drives.


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First lets talk about what a Fusion Drive is and isn't.

The word Fuse gives us a clue here as binding two things together. In this case we are linking a spinning disk HD device with a SSD device using a method in software so the two devices are seen as one.

Binding drives is not new UNIX & MS Widows have done it for a few years now (disk spanning & RAID). But what Apple did was go to the next level by moving more accessed files onto the faster device (SSD) and less used files are placed onto the HD, making better use of the storage.

The bugaboo with fused drives (all) is the risk of loosing data if one of the drives goes south. This is were its important to have a good backup strategy.

The other direction is to use a SSHD (hybrid drive) in this case the single device is a standard HD but it has a SSD unit as well that act as a deep cache. Similar to the Fusion were the higher hit files are held in the SSD cache the original file is still present on the HD.

The third drive type is the WD Black2 which again is a single device but unlike the SSHD is more like the Fusion setup were a HD and a SSD can be combined into a single drive. Presently this drive is only useable in a MS Windows laptop.

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Ones options are likely to be limited here on what you buy is what will likely be the limit of the system. Apple does not offer after sales upgrading. While some 3rd parties have offered options presently there is no storage upgrade options for the newer thin series of iMac's by any 3rd party. Some had shown early samples a year ago but nothing has happened since then.


So cutting to the chase here: If you are thinking of buying a system which has upgradable storage options then you want a Mac Pro not an iMac. We have bit the bullet and have stopped buying iMacs and now are buying Mac Pro's or Mac mini's.


I wasn't asking about software or what the definition of fuse might or might not be. I can read the marketing crap about Fusion on apple's website. Terminal ok, I got that, really I do. The introductory sentence in the original post was I'm not asking about software. Thanks for "fusing" lots of unwanted words into your post about back-up and other needless statements. And above all I don't care about Western Digital drives or external storage options. If we could focus, OK

We're asking about hardware, and highlighting the fact that the teardown of these machines are lacking detail.

Additionally, we're not asking what's feasible for you or me. I don't care what you think is or isn't a family car or the dump truck, sorry but in some 500+ words the only interesting statement that was made regarding the internals of the iMac 27" 5K was:


"There are three on-board storage connectors, two are SATA one is proprietary."

How do you know there is 2 SATA connections? What is the source for this information?


Greg you are clearly getting agitated here. The way you asked the core point it implied you didn't follow what a Fusion drive was.


The first issue is you can't buy the custom SSD units Apple uses. So altering your iMac after the fact is not going to be easy if even possible. If you get a SSD only model then I could see you opening the system and putting in your own HD unit but thats it. As to the specs of the Apple SSD units there is more than the physical devices here there is also the firmware that is on the SSD unit that needs to be Apples.


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