I have an Apple Samsung 256 GB SSUBX SSD which when installed in a 13" MacBook Pro Retina 2014 delivers 1,300-1,450 MB/s Read-Write, whereas when installed in newer 15" MacBook Pro Retina 2015 only provides 650-750 MB/s (both measured with Black Magic Design Disk Speed Test).

Makes somehow no sense to me... Ideas?

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  • What tool measures the speeds? In Disk Utility and System Information - what's the negotiated speed between the controller and the logic board?
    – bmike
    Sep 2, 2018 at 0:02
  • As I wrote, I used Blackmagic’s Disk Speed Test, the app virtually everyone uses to determine disk speeds. See here: itunes.apple.com/de/app/blackmagic-disk-speed-test/…
    – Dr. Woo
    Sep 3, 2018 at 8:29
  • Sorry. Great edit. The second point on link speed negotiation might be key for your investigation.
    – bmike
    Sep 3, 2018 at 16:13

1 Answer 1


I should mention that I had no access to that 15" MBPR, but that that performance data was reported to me by the customer who bought this SSD from me. Looks however as if that MacBook had some serious repair damages, as the customer has now confessed. That said, I guess we can ignore my question.

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