SSD for Mac Book Pro 2012 optical disc drive I'm about to upgrade my MBP mid 2012 with two SSD drives instead of the stock HDD and optical disc drive. I read on different forums that the optical drive link with the motherboard is only SATA 2 and that this will eventually cause problems with a SATA 3 SSD.

I, however,  see lots of videos and articles where the optical disc drive is substituted for an SSD. Are those new SSDs SATA 2 or is this not an actual issue (with the bandwidth)?

Can I use a SATA 3 SSD instead of the optical drive? Can I "switch down" a SATA 3 drive to SATA 2? Or do I need to find a SATA 2 SSD to use in the optical drive?

Added

I specifically want to instal two Samsung EVO 850 500 GB in my old MBP.
SATA interfaces are backward compatible so you can use a SATA III drive on a SATA II/I port.

From the SanDisk Knowledgebase:


  SATA II specifications provide backward compatibility to function on
  SATA I ports. SATA III specifications provide backward compatibility
  to function on SATA I and SATA II ports. However, the maximum speed of
  the drive will be slower due to the lower speed limitations of the
  port.


I have actually done the upgrade you are describing (though with one SSD and a spinning drive in the optical bay).  There are no issues with SATA compatibility.