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IronPython allows multi-threaded code to use multi-core processors. Multi-threading allows you to take single threads through dedicated cores. It is taking advantage of the multiple cores to run each thread differently. Threading does not happen at the same time, but rather keep switching based on time allocated per thread or the thread being over(download in this case) altogether. Multi-processing is a win-win, no core is burdened as they share the load while you get a faster experience.