SSD for Mac Book Pro 2012 optical disc drive

Question

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.

Answer 1

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.