imac early 2009 negotiated speed of 1.5Gb/s

If your Sandisk SSD uses Sandforce it will only run at SATA 1.5Gb speed due to a well known conflict with the Nvidia MCP79 controller in your iMac. You should return it and get a Samsung or other brand that doesn't use a sandforce controller.

Don't know. You should probably contact Sandisk and see if they can offer any advice. I have SSD's from Samsung and OWC and neither has a conflict with the Nvidia controller.

I also installed sandisk ultra II with marvel controller to iMac early 2009 today, and also have 1.5 link on optical bay. Have also done clean instal of el capitan and reset Nvram

don't really want to tear this machine down again, any help appreciated.

thank you, this saved me the hassle of trying that....l put the same type of drive in my early 2009 macbook 2 weeks ago and that runs at 3Gb...will check the controller and report back

I checked my macbook purchased in early 2009 which has in December had a 120 gig sandisk fitted. The 120 gig uses the marvell 88SS9190 as opposed to the 88SS9189 used in the drives we are having issues with. However it seems crucial MX100 dives also use the 88SS9189,

see below 3Gb and the drive is fitted to the hard drive connector.

NVidia MCP79 AHCI:

Vendor: NVidia

Product: MCP79 AHCI

Link Speed: 3 Gigabit

Negotiated Link Speed: 3 Gigabit

Physical Interconnect: SATA

Description: AHCI Version 1.20 Supported

SanDisk SDSSDA120G:

Capacity: 120.03 GB (120,034,123,776 bytes)

Model: SanDisk SDSSDA120G

Revision: Z22000RL

NVidia MCP79 AHCI:

Vend

Revision: Z22000RL

Vendor: NVidia

Product: MCP79 AHCI

Link Speed: 3 Gigabit

Revision: Z22000RL

Called sandisk...operator informed me that drives will not run at SATA 2 with MCP79. i tried to correct them on the controller change to marvell but they were restricted due to confidentiality to have any detailed discussion on marvell. I asked why my 120 gig worked at data 2 in the macbook and this was a surprise to them!! they are going to check with technical engineer and report back in few days...

Hi Daveeyt, did you get a response from the technical engineer in the end?

HI. Sandisk were hard work. I gave up with them in the end. Their drives would not negotiate sata 2 in imac. In the and i bought a crucial mx200 and the imac runs consistently at Sata 2. Both the 480gig and 120 gig Sandisk drives run at Sata 2 in my 2008 MacBook with same NVIDEA

controller as the iMac. Software issue with Sandisk was my conclusion.

Hi again - thanks for the response. Well, from the information I have collected, there seems to be a peculiarity between what doesn't work for the iMac but works for the MBP even when both have the same nvidia MCP79 controller! If you are interested, or for anyone else following this thread, you should check out the following thread:
Best COMPATIBLE ssd for NVidia MCP79 chipset?

In the end, I decided going for the OCW Mercury Electra 3G ssd because no M500's were in stock. As far as I know, those are the only two drives that have consistently negotiated the correct sata 2 speeds in the iMac nvidia MCP79 sata controller implementation. I am referring specifically to the iMac 9,1, in case anyone is interested.

Cheers!

HI. The different negotiated speeds of the sandisk is consistent as the sandisk drive is swapped from MacBook to iMac(9,1). Only apple,sandisk or Nvidea have a chance of knowing the root cause to this, and that ain't going to happen for a 6 year old computer . The corrective action was to remove sandisk from the iMac and fit a crucial MX200, this consistently negotiates SATA 2

The sandisk extreme II with Marvell controller achieves Sata 2 in MacBook and only Sata 1 with iMac