I want to upgrade my old drive with an SSD, and the one being recommended to me by the local Mac-friendly store is the Crucial 256GB M4 SSD, which is Sata 3. But I'm told that Macs of my vintage aren't Sata 3 compatible.

On the other hand, I'm also told that the Sata 3 drive will automatically scale back to Sata 2 if that's what surrounds it, and so it should work fine.

I don't know who to believe!! Any thoughts?

SATA III drives will work in older machines but will run at SATA II speeds.

Thanks Andrew!