i have a crucial bx200 installed in my mini 2009, same chipset. It runs at 3.0 gb/s negotiation speed all the time no problem. I'm running El capitan. However, from what i read and noticed you have to allow the 'Active Garbage Collection' time and space to take care of the disk or it will throttle back to 1,5 gb/s. So don't stuff it and allow it Some idle time at the end of the day. It works for me. On a Mac, press the Options key while powering on to enter the Startup Manager screen. Leaving the Mac on that screen provides the SSD with power but keeps it in an idle state so Garbage Collection can function, just like the BIOS screen on a Windows laptop.