Yes, you'd need 4x parallelism for a 2x speedup (16x for 4x, etc). But there's plenty of situations where that would be practical and worthwhile (think a build

Yes, you'd need 4x parallelism for a 2x speedup (16x for 4x, etc). But there's plenty of situations where that would be practical and worthwhile (think a build and test cycle that takes ~1 hour each and can't be meaningfully parallelised further).