robricc carpal tunnel
Registered: 30/10/2000
Posts: 4931
Loc: New Jersey, USA
I'm typing this from memory, but in some 13" MBPs, although the controller for the optical bay is capable of SATA 6Gb/s speeds, the cable is only designed for 3Gb/s. Possibly because the optical drive supplied with the machine is only rated for that speed.
Is there a way for you to force the SSD to the lower speed?