I recently replaced my broken SuperDrive with an OCZ Agility 3 120GB SSD with the following specs:

  • 2.5" SATA 6Gb/s
  • SandForce 2281 Controller
  • Read 525Mb/s
  • Write 500Mb/s
  • 85K IOPS

I have an Early-2009 24" iMac (9,1), and I purchased a caddy to place the drive in in order that it can sit where the SuperDrive was.

My iMac has a SATA2 bus, but after connecting the SSD it will only connect at SATA1 speeds. I knew that the SuperDrive used to use this speed, but accepted that it was because is was simply an optical drive that could not push the speeds to saturate a SATA1 controller, so why bother with anything better.

However I expected the SSD to link at the SATA2 speeds that the bus supports.

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I have the latest firmware on the drive itself, and on my Mac, I have reset my PRAM, and I don't know what to do next. Why does the SSD not connect at SATA2?

I accept that I cannot get SATA3 like the drive supports, but some initial testing using a disk speed test tool suggests I am only getting just over 100Mb/s write and 145Mb/s read, which is a mere 20-80% more than the regular drive gets.

I cannot just swap the drives over, as it's not like the MacBook Pros that use 2.5" drives. I have done a lot of Googling that suggested a firmware fix for MacBook Pros solved the same issue on those machines, but no luck for my iMac.

I have just put a normal SATA2 drive into the optical caddy, and it comes up at 3Gb (SATA2) just fine. So it seems it's something about the SSD that it doesn't like. Controller? I wouldn't have thought that it cared what was connected, so long as it was SATA?

  • Apple is known for loading custom firmware on all drives it installs - perhaps your mac is downgrading to lower speeds since it can't tell what drive is installed. Is it possible to reach out to the vendor to confirm you have their latest drivers on the SSD?
    – bmike
    Apr 19 '12 at 18:15
  • Also - did you reset the NVRAM to ensure the device tree gets rebuilt after the repair?
    – bmike
    Apr 19 '12 at 18:19
  • PRAM & NVRAM reset, it refuses to go above 1.5Gb on any port, caddy or not. Confirmed latest drive firmware.
    – stuffe
    Apr 19 '12 at 18:36

Looks like a known problem with the SSD. OCZ has a firmware on their forum that will fix the issue. See the post "Changing SATA speed on your "3" series SSD." in this thread.

This portion of the instructions only applies to OCZ "3" series SSD's - Vertex3, Agility3, and Solid3 - all sizes. Some SATAII motherboards, when used with one of the above drives will downgrade the drive to SATA1 speeds. We find this mostly on Nvidia chipset motherboards for PC and Nvidia chipset based Mac's. To resolve this, we have a tool that will set the link speed to be locked at SATAII and improve performance. This can be reversed when you update your motherboard/system so you can have the full SATAIII speed again.

Installing the firmware involves burning a Linux LiveCD so I hope you have a computer with the optical drive still in.

  • Thanks, I will look into this further - I have seen various threads on there, but none that identified the problem so emphatically.
    – stuffe
    Apr 21 '12 at 17:05
  • Thanks Tyr, I had seen that thread before but not noted the specific section you pointed out - I thought it was just for updating your firmware which I already knew to be the latest. I am now running at 3Gb just fine.
    – stuffe
    Apr 22 '12 at 11:21

Sandforce drives have had many issues with Macs and should be avoided with Apple hardware. Go for non sandforce controllers like samsung, crucial, or the vertex 4

  • Without any references this statement could easily be a rumor. Can you add some references to actual problem reports?
    – nohillside
    Nov 26 '12 at 18:22

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