510 SSD use in 17' MBP 2011, Drop speed even lower than Sata 2

[idata]

I bought my 17inch macbook pro in may 2011. I replaced hard drive to Crucial M4, Didnt compatible. Then changed to Intel 510 250Gbs. It much better then M4. However, I still have problem with unstable and one of more serious problem. The sata 3 negotiated link speed usually is 6Gbs. My ssd only run 3 Gbs. And really slower than nomal.This is image shows evidence.Is anyone can give me the answer? Thank you!

[MBall5]

I know there are ssds sold by Mac that are specifically meant to work with their systems, my suggestion on this case will be to contact Mac and see if they have any recommendation or if they can confirm if your system does support the ssd that you have.