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Model A1419 / EMC 3070 / Mid 2017 / 3.4, 3.5 or 3.8 GHz Core i5 or 4.2 GHz Core i7 Kaby Lake Processor (ID iMac18,3) / Retina 5K display. Refer to the older iMac Intel 27" Retina 5K Display (Late 2014 & 2015) guides as the system is very similar.

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bigger PCIe in Fusion Drive?

Hello there!

Now I have standard 2TB Fusion Drive in my iMac 5K 2017.

I want to install bigger PCIe drive. Why? Because I have one... 1TB from my old (dead) MBP15 mid15. I have read somewhere that apple's 1TB drives are much faster than 128GB or 256GB

I saw a lot of movies about opening iMacs, changing HDD, PCIe etc.

Problem is that I don't know how works management Fusion Drive. Actually I know there are two phisical drives and they are seeing as one. But how to replace?

Do I have to copy some data?

I hope I will find an answer here.

Please help :)

Answered! View the answer I have this problem too

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If you are looking for performance than converting a Fusion Drive'd system to a dual drive setup where you've replaced the wimpy PCIe/NVMe SSD to a bigger and faster SSD will gain you a lot!

But, just boosting the Fusion Drive with a bigger caching SSD won't get you that much gain.

I would first check to see if the SSD yo have from your MacBook will even work as Apple jumped around a bit with different interface standards and in the case of PCIe/NVMe from x2 to x4 lanes. So while a two lane SSD will fit in a four lane system (only getting you two lanes of performance) the that can't be said the other way around in all cases.

Give this a good read The Ultimate Guide to Apple’s Proprietary SSDs check things out before you start the process.

Then also review this guide as it explains the needed process to get to the SSD. And before you even start make a backup of all your stuff! As you''l need to scratch the HDD down reformatting it to break the Fusion Drive setup so you can add in the blade SSD. and lastly make a bootable USB thumb drive with the macOS you are currently using as its a lot better than trying to work over the Internet recovery and given your systems age its likely the recovery will install the original OS the system was sold at not one the newer ones which adds a bit more complications!

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Hi Dan!

Thank you for your answer.

Guide looks good 👍 iMac 18,3 and MacBook Pro 11,4 have the same interface - 8.0 GT/s PCIe x4.

But all that stuff with data makes me scared... I was thinking that I don't need to do all that things. Plug and play... Merge drives to one and voila :)

On the iMac we have 4 user accounts... and almost 1,3TB of data. Lot of work. Second Mac in Target Disc Mode via Thunderbolt?

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@thinker45568 - This is looking harder😩

Multiple user accounts will require separate drives or within a drive independent partitions so you don’t flatten the file space.

Then once you create the new accounts you can then transfer each volumes data into the correct user account.

You really need someone local who has the skills and can put their hands onto the system to help you here.

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Good evening,

Based on some very brief research, you would be correct the computer sees them as one. The best way to do this would be to copy all your precious stuff/do a time machine backup to an external drive. Once that is complete, remove both drives, install your PCIe drive, and connect up a USB keyboard to enter recovery. You'll need that keyboard to navigate the menus, and it has to be a wired one.

Once you reinstall macos on it, you're good as gold! Just be sure to check with the wonderful internet before you take my advice as I am no expert and have failed (a couple of times) at reinstalling macos which bricked some machines :). however this isn't based on my experience but rather research on imacs.

At this point I'm just rambling, but good luck :)

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