I just replaced my old HD from a late-2009 iMac with a new Samsung SSD 850 EVO 1TB. It was installed by an official Apple repair store but I am worried because it seems slower than my new macboook pro (also with SSD) I tested with Blackmagic Disk Test and it:

  • Writes 253 MB/s
  • Reads 268 Mb/s

Official specs say it should:

  • Write 520 MB/s
  • Read 500 Mb/s

And it seems from reviews they get numbers close to official ones.

I checked my SATA Chipset in the iMac and it says: "Link Speed: 3 Gigabit".

Does this mean that 3000 Mb/s (Megabits) are 375 MB/s (Megabytes) and it cannot transfer faster (even though the SSD is faster)?

1 Answer 1


I would make sure that TRIM is enabled. Without TRIM, SSDs will run slower. I use Trim Enabler to turn on TRIM on my Samsung SSDs.


Nowadays it can enable TRIM without disabling kext signing.


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