Managing multiple processors requires a lot of overhead work on the part of the operating system. Because of this, having twice as many processors in a computer doesn't double its processing capability; instead, doubling the processors might improve the computer's speed by only about 50 percent. Depending on your operating system, there is also a point of diminishing returns, past which additional processors won’t give you much additional performance.
How exactly do you understand that past here? Is it functioning as a preposition or an adverb?