I am looking at cpu's like i5-3317U with 2 cores and 4 threads, and then seeing cpu's like i7-3517U with 2 cores and 4 threads. Aside from speed, cache size, and minor things, what's different? They don't differ the way an i5 and an i7 desktop chips do. They look like the same chips with slightly goosed features. Am I missing something big?