First what benchmark are you using? ATTO disk benchmark is what is used for the advertised benchmark. This SSD has a Sandforce controller and they do better with compressed data. Some benchmarks out there use uncompressed data so you will not see the advertised numbers.
Also you need to make sure the SSD is aligned to 4K boundaries. If you have Windows 7 or 8 and used disk managment to format the SSD you should be good to go. You can download AS SSD to check alignment if you are not sure. When you open the APP if the numbers in the top left show in the color Green and it has a OK beside it the drive is aligned properly.
