Upgraded to 512GB SSD, now SSD link width down to x2 from x4?

"It's the part you put in is only a PCIe x2 unit not a PCIe x4 which is why the lane width dropped.

The newest version of the SSD is hard to come by and it will be more expensive. So far Apple doesn't offer it as a spare only as a swap out (you need to send the old one back) and it needs to be the same. Hopefully this control will end soon as the newer models don't use the same blade type of SSD. In any case it will be costly!

Update (02/08/2017)

Adam you'll need to get into the system profiler service to check the new SSD's firmware comparing it with your older SSD.

Open About This Mac and click on the System Report button. Click on NVMExpress and SATA/SATA Express sections, enlarge the window so all of the info on the right is visible snap a screenshot of each and post it here so we can see what each has.

As a reference review this question and what Eduardo encountered: Upgraded my SSD, Was it not suppose to keep same read/write rates?"

"I have had issues with my upgrade to Samsung 970 Pro 1TB with Sintech adaptor of lanes and sink speed dropping.

See here.

Please confirm if this PCIe SSD would work with my 2015 system

I found a reset to PRAM allowed it to return to the full 8GT/s and 4x link width.

Obviously you will not be able to get a faster or wider link than the slowest bit of hardware in your chain.

eg I put the 512GB SSD from my 2015 15” rMBP into a 2013 iMac and despite the SSD being capable of 4x it will only get 2x link width because the iMac is only capable of 2x.

Point here is for a machine that you know is capable of faster, the PRAM reset fixed my issues twice."

were u able to figure out the cause? same here lane dropped after upgrading late 2013 MBP from 256GB (A/00) to 512gB (A/06)

is there any way to upgrade the imac2013 from 2x lan to 4x lan ?