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Model A1419 / EMC 2806 / Late 2014 or Mid 2015. 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (ID iMac15,1); EMC 2834 late 2015 / 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (iMac17,1) All with Retina 5K displays

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iMac late-2014 SSD blade upgrade - link width hasn't increased

I just replaced the 128 GB Apple blade SSD in my late 2014 5k 27" iMac with a 500 GBg Apple blade SSD (SM0512L) breaking the original Fusion Drive set. I also replaced the 1TB HDD with a Crucial SSD.

The Crucial SSD via the HD SATA port is connected at full speed (6.0 Gb/s), very happy.

But the new Apple SSD shows a Link Width x2 (@5GTs). The SSD is a 2018 model and PCIe x4 - why am I only getting x2 (and hence lower speeds)?

Is it because my iMac doesn't support PCIe x4 ? The new SSD also now shows under NVMe. I've spent the past few days (and literally hours) reading through various forum postings, but can't find anything about my particular iMac model and the 'support' for Apple SSD's.

The speed for the new SSD is much better than the original - 730 for both read/write, compared to 290 write, 580 read on the older model, but I was expecting double those figures - probably stupidly.

Anybody know what the late 2014 27" iMac actually supports?

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Did you review this helpful listing: The Ultimate Guide to Apple’s Proprietary SSDs?

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Yes, its my bible :) It states that the late-2014 27 inch does support pcie 2.0 4 lanes... but I've seen people comment on other forums that it doesn't. And as I'm not seeing 4 lanes in the link width, something definitely isn't right. I'm wondering if I did something wrong in the install and the SSD connected at a lower link by default? I didn't install the OS to the new SSD 'externally', I did it via recovery once I'd fitted it.

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The Ultimate Guide article has since been updated to correct that the late 2014 iMac uses 2 lanes.

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@brianc - If you have a way, I would clarify a 4x blade will work but won''t offer more than x2 lanes. Which is the real issue here.

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That iMac does not support 4 channel, I'm going to have the same problem.:-(

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I think your issue maybe the systems firmware level and the MacOS version you are running. I don't have this system so I can't be sure, but I would get to Sierra if you are not there now and then give High Sierra a try. Both are updated when you do a OS upgrade.

WARNING! High Sierra will automatically switch your boot SSD drive to APFS (it may also alter your second SSD drive (haven't tested that). So keep that in mind!

Update (04/17/2018)

Here's a useful diagram:

Block Image

As you can see there are two paths for ACHI services the legacy SATA (Red path) and AHCI (Orange path).

I don't think Apple uses 4 lanes in ACHI mode. It would seem to be a waste as SATA to block translation services on the SSD (AHCI controller) can only go so fast, and technically it can't exceed 6 Gb/s.

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Sorry I should have said, The version I installed on recovery was High Sierra - could it be that the right firmware wasn’t already in place? Or would the install of High Sierra have sorted that? Is it worth downgrading to Sierra first then updating to Hgh Sierra?

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Which model do you have? iMac15,1

Sorry the firmware would have been updated as well as the NVMe driver. Apple made changes to both in High Sierra so I was hoping it would have helped.

So it sounds like the older systems (PCIe 2.0 x4) can support the newer PCIe/NVMe (PCIe 3.0 x2 or 4) SSD's but not offer the four lane support some SSD's offer (PCIe 3.0 x4).

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Yup its the iMac15,1 - base model. The SSD is APPLE SSD SM0512L and the firmware is CXS7CA0Q. I'm pleased with the jump so far in speed, was just trying to understand why I didn't get 4 lane support. Thanks for the info !

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Just to clear up a slight error here: The firmware I was speaking about is the systems EFI. You'll find it under 'About This Mac' > System Report. Then clicking on the 'Hardware' tab to see the Hardware Overview under 'Boot ROM Version' as an example my MacBook Pro 2012 shows MBP91.00D7.B00.

The SSD also has its own firmware which is what you posted (CXS7CA0Q).

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Did you ever get confirmation on this? My new 1TB SSUX also only gets 2 lanes but I get 4 on my same time period MBP. Strange indeed." The 21.5″ iMacs only support PCIe 2.0 x2 connections, but the 27″ iMacs support four channel PCIe 2.0 drives and can see speed improvements from using later Gen. 4 drives."

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Nathan will be eternally grateful.
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