Specifically this would be limited by the computer hardware and the single threaded performance. The higher the single threaded performance, the better any CPU core will be able handle a larger load. More CPU cores can help offset other work for other threads, so having more cores can help, up to the limit of the single threaded performance for any one thread on any one core.
More efficient code can often go alot lot further for alleviating performance pains.
Just as example, this script was causing high performance impact on client computers and we got some complaints. I've re-written the code to be much much more efficient and it causes a much lower performance impact.

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