[thesimp]

I fondly remember Fractint (https://www.fractint.org/). And these days I'm amazed at what it could calculate with the very limited CPU cycles at that time. I'm not sure how to compare a 386 running at 25MHz with my AMD 5950x that I have now.

[eru]

Fractint did a lot of clever tricks, especially for the Mandelbrot fractal. For example, I remember they exploited that the Mandelbrot set is connected. So that means that if you found that the border of any rectangle is either completely inside or completely outside the set, you don't have to check the inside.