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Background: I have a MacBook Pro (late 2011) with a SATA III 6Gb SSD installed in place of the optical drive. Sources say this configuration should work, but I've been having problems (read/write failures, spinning beachball, etc) of exactly the sort you would expect if a SATA II bus was trying to operate at SATA III speeds. I'm beginning to suspect that my laptop may have the issue reported for early 2011 MacBooks that made them unstable with 6Gb SATA III. The best solution would be a SATA 2.0 drive, but the drive I have is already in hand.

Is there any way (preferably through software) to set the SATA Negotiated Link Speed to 3Gb instead of 6Gb?

Edit: The SSD in question is a Seagate/Samsung 850 EVO (MZ-75E250B/AM), if the solution is drive-specific.

  • Have you verified that your optical drive is, in fact running (or thinks it's running) SATA III? – agentroadkill Jul 24 '15 at 3:10
  • @agentroadkill The interface reports (in System Information) "Link Speed: 6 Gigabit" and "Negotiated Link Speed: 6 Gigabit" for the optical bay. The SSD in the optical bay is a SATA III 6 Gb drive, backwards compatible with 3Gb and 1.5Gb. Other than that, I don't know how to verify that it's actually running SATA III. – Robert Jul 24 '15 at 23:29
  • If System Profiler reports SATA-III speeds, I take it at its word. My MacBooks generally seems smarter than me. – agentroadkill Jul 24 '15 at 23:40
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So, having verified the drive is, in fact running at SATA-III speeds, it looks like this post describes doing what you need. Be aware it requires a DOS environment to run, so you'll likely want FreeDOS with the .iso loaded already.

I haven't used this, so I am unable to verify results. Attempt at your own risk.

  • Thanks! Unfortunately my drive is a Seagate/Samsung and that utility is only for HGST drives. I'll mark it anyway if I don't get a better answer. – Robert Jul 25 '15 at 5:32
  • Thanks for the feedback, though you shouldn't feel the need to mark answers if they don't address your question, it may confuse others and discourage people from researching your question more closely. – agentroadkill Jul 25 '15 at 10:41
  • I must say I'm a big fan of the Samsung drives myself (that's what I use). They have a huge collection of software specifically for their drives you may want to check out. I don't quite believe the HGST documentation; it would seem unnecessarily difficult to re-write a firmware driver then make it only work with a given brand (though that doesn't really surprise me). It may be worth trying anyway; it gives you the option to undo it if something happens. – agentroadkill Jul 25 '15 at 10:45

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