Depends on how many words are in the dictionary. Personally, i like pyrit with cuda... on a 8 core amd 2.4ghz & a gts 250, i get 10,000~ pmk/s
uhh.. completely borked numbers here, but 3gb is 3221225472 bytes.. so uhh.. / by 10000, 322123 seconds, 90 hours? But im bad at math, i could be wrong.