On my grossly overpowered workstation, I can only crank the number of workers in the Mandelbrot demo to 20 [1]. Attempting to go beyond 20, the console reports:

    RangeError: out-of-range index for atomic access

That said, 20 workers is about 11x faster than the single-threaded version.

[1] https://axis-of-eval.org/blog/mandel3.html?numWorkers=20