iMac negotiated link speed

My IMac has the buggy NVIDEA MCP 79 SATA 2 controller which doesn’t play well with sandforce controller, so was confident would be ok with the Marvell controller now being used in the ULTRA 2 SSD of which I purchased the 480Gb drive. However only get SATA 1 link. I see on the data sheet there is one of 2 firmware listed as correct due to later drives having a slight hardware difference, anyone know what this difference is, or can help to explain why only SATA 1 connection. I also bought a 120 gig drive for my 2009 MacBook which has same NVIDEA controller and that runs at 3GB (SATA2)

Any help appreciated.

the problem is the nvidia sata controller. it is buggy and does not play well with newer SSD products. the link speed negotiation issue can occur with any SSD using any controller. if you google you will see reports from every ssd manufacturer out there and can be hit or miss. nvidia and apple are not addressing the issue because the chipset is obsolete so honestly there is not a lot you can do about it.