I wondering if I put my 1600Mhz 8Gig (4gigx2) modules in a Macbook Pro 17" 620m (2010 model) if the speeds would be automatically reduced to 1066Mhz? I'm just asking because I don't want to damage the computer. I've read that this will happen, but I just want to ask around before hand :).
The frequency rating on RAM is analogous to the top speed of a car, if it's max speed is (for example) 250 km/h, it can drive up to 250 km/h, but it won't break if u drive at 25 km/h.
Same for RAM. As long as it's the same DDR3 Standard, it will run, regardless of how high the max clock speed is.
For example, my MacBook Pro mid 2010 13" (MacBookPro7,1) did not support Hynix 4GB PC3-12800 DDR3 1600 MHz sticks if used alone or 4GB+4GB, they work only if coupled (2GB+4GB) with pre-installed 2GB 1033 MHz sticks from Samsung.
XAleXOwnZX already answered, but I'd like to confirm that this indeed works with you 2010 MacBook Pro. I've had a 13" 2010 MacBook Pro and upgraded using 1600 MHz RAM.