This is an oversimplification. Some compute intensive parts can get significant speed ups through careful use of data parallelism (such as SIMD). Others needs

This is an oversimplification. Some compute intensive parts can get significant speed ups through careful use of data parallelism (such as SIMD). Others needs parallelism at the thread level. Etc. Optimizing for memory patterns is important as is trying to keep the working set within a near-level cache.