Model A1418 / Late 2012 / 2.7 & 2.9 GHz Core i5 or 3.1 GHz Core i7 Processor

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iMac 21,5" 2012 dual hard drive

Hey guys,

I’m about to upgrade my iMac 21,5“ Intel 2,7 GHz (late 2012) to a 500 GB SSD. It would be most preferable to keep the 1 TB HDD that currently holds the OS X as internal hard drive for storage purposes.

On the iFixit website I’ve stumbled upon the „iMac 21,5“ and 27“ Dual Hard drive Kits“. However, these are meant for iMac 2011 only as far as I understand?

Is it possible at all to upgrade a 2012 iMac 21,5“ to a dual hard drive?

If so, does the aforementioned Kit work for the 2012 iMac as well and can I just apply the 2011 iMac instructions?

Thanks a lot for your support! Your website and the whole DIY project is brilliant!

Kind regards


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Sorry Simon, the dual drive kits you are pointing to are not suitable for the newer 'Thin Series' iMac's.

Your system does have a second drive port its just setup for a blade SSD unit but I must warn you this is a very big undertaking to add the SSD. Follow this IFIXIT guide: iMac Intel 21.5" EMC 2544 SSD Replacement.

You'll need to buy the correct SSD unit and you will need the special tools to pull the display off and replacement adhesive tape strips to remount the display.

If this is your first time opening an iMac I would recommend leaving this to someone with more experience.

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Thanks for your reply!

I did get the adhesive tape and an opening tool.

What do you mean by "correct SSD"? The SSD I'm going to build in is a Crucial MX100. Do I need an adapter or something?

Thanks for your advice!


Ive just read through the guide you've linked. I don't think that is what I am up to: I want to replace the HDD hard drive (1 TB) by a Solid State Drive 500 GB. The guide applicable is iMac Intel 21.5" EMC 2544 Hard Drive Replacement, right?

Thank you!

PS: Is it preferable to also upgrade RAM while you have the iMac opened anyway?


Your question implied you wanted to keep your HD and add a SSD. Thats possible by just installing a blade SSD as I explained. I don't recommend swapping out the 2.5" HD to a SSD in this series. If you want a faster drive setup I would go with a Seagate SSHD (hybrid drive) or go with a WD Back2 (dual drive). That way to hang onto the storage space a HD offers with the benefit of the SSD for a deeper cache.


Thanks Dan!

Why wouldn't you recommend a pure SSD? Because of the low storage space of 500 GB?

The thing is that since updating to Yosemite my iMac takes several minutes to start up (grey loading screen). I don't know whats taking it so long or what its doing when the loading screen appears. I reinstalled the OS and constantly repair the hard drive using the customary hard drive utility, but nothing seems to help, on the contrary, it seems to be getting worse and takes up to 5 minutes lately!

Thats why I thought upgrading to SSD would be a good idea..


You may want to do some deeper testing as its starting to sound like your HD is going vs a slow drive.


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I have a follow up question for this string. I am trying to do the same upgrade, ie add memory 16G, and a 250G-500G SSD drive but keep my 1T fusion drive. Can I do both? Have the SSD be the boot drive and the Fusion a second internal drive. First, is it physically possible. I assume the SSD has to fit next to the RAM under the processor board. Second, how do I move all the software and boot to the SSD and use the Fusion for photos, movies etc. I have a 13,1 late 2012 imac with 1T Fusion and 8 G ram, 2.9 HZ processor.

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A Fusion Drive is two drives which are 'fused' together so combined they look like a single drive logically.

So a system which has a Fusion Drive has TWO drives already within the system: a HD and, a SSD.

Sadly your system only has two drive ports which are both in use so you can't add a third drive.


A few follow up questions. Are they literally fused together or is one just using the port next to the memory simms and the other on the front side. What is the current SSD size and can I just replace that drive and expand the storage. Can I expand the SSD drive size and use it for more storage or am I just stuck. I guess the other options just to replace the fusion drive with an SSD drive? Not sure how much more performance that will give me. I do plan to upgrade the memory too. If they are literally fused or attached together than what about the pci port next to the memory. Is that not available.? If I do swap the drives, how best to move the software and data. I was told just use time machine back up but not sure how that works if the drive is blank on boot up.



I think you got things twisted about. Port A (SATA) has the HD and Port B (PCI) has the SSD thats are there is for ports. Then within the OS Port A & Port B are made to look logically like a single drive. This is how an Apple Fusion Drive set is created.

Now lets look at two other drives a SSHD hybrid which is a single drive which has within it a deep SSD cache (8 or 32 GB depending on the drive) Seagate Laptop SSHD. This SSD cache here is only visible from within the drive its self so the OS does not see it. It only uses one port and the SSD is not seen.

For a short while a second type of hybrid drive was on the market: Western Digital Black2 dual drive unlike the SSHD this drive was really two drives that used one port! Sadly it did not sell well as many people didn't understand what it was. It is no longer being made.


As to your root question How to Improve Performance with the new 21.5" Thin series iMacs

I would think long and hard here before attempting to do any upgrading as this series as they are much harder to open than the older series.

To add to it depending on your exact model you may not be able to any memory as some have soldered memory. If you have an HD model only model your system may not have the PCIe port hardware to even install a second drive.

I would strongly recommend getting an external Thunderbolt RAID drive as the better direction for more storage as an example this is what we use: OWC - Mercury Elite Pro RAID Enclosure.

I would also recommend you clear out and much as you can from your HD or SSD (or Fusion Drive) as a full drive will slow your system down. I recommend leaving 1/3 of the drive free for anything 256 GB or smaller and 1/4 for 512 GB or larger.


If your systems memory is low and you can upgrade it, I would attempt that, but this is not an easy upgrade!

You may want to think about selling your system to get a new unit which has more memory as well as a larger PCIe SSD drive. Even if you get a SSD only model adding the HD is a lot easier! Than upgrading the memory or SSD.


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