Much of the terain genertion consists of doing the same thing for every single column or block in a chunk. This sort of computation is much faster on a GPU as GPUs are massively parallel. High end GPUs can execute up to 30,000 threads simultaneously, which would allow them to generate every block in half a chunk in parallel or every column -in over 100 chunks in parallel. A naive comparison suggests a 800MHz a GPU with 15,000 threads can execute parallel +in over 100 chunks in parallel. A naive comparison suggests that a 800MHz GPU with 15,000 threads can execute parallel code 250 times faster than a 3GHz CPU with 128 bit SIMD. Obviously we want to harness that power.