This guy has some incredible hacks, such as the mandelbrot for BBC Micro (in 6502 assembly) that uses a lookup table for squares of numbers, and takes advantage of the connectedness of the colours:

"It turns out that Mandelbrot and Julia sets have the property that any area which is completely bounded by a colour contains only that colour. (Because it’s simply connected.) (No, I don’t understand a word of that paper.) So the program recursively traces out the bounds of boxes, and if all sides of the box are the same colour it fills it and doesn’t recurse in."

http://cowlark.com/2018-05-26-bogomandel/index.html

Also a bootloader for the GPU of the rasperry Pi: http://cowlark.com/piface/