Changing my RAM timing

[JSD13]

I have two DDR 3 G-Skill 2GB sticks. It came with timing of 9-9-9-24. I changed the timing to 8-8-8-21, but do I need to edit any other settings along with it or is that all?

 

[dokk2]

check data sheet for voltage specs..

 

[JSD13]

What does this mean?