In 1990 I wrote a Mandelbrot set generator for the HP9000 series 835 at the lab where I worked as an undergrad. It rendered directly into the frame buffer on Turbo-SRX. We used to let it run for hours. We'd come back later, or the next day to see the pretty pictures.
I can't remember what the resolution on the second head was, but I can't imagine that it was more than 1280x1024, if that (anyone remember)? Anyway, I ported the code to linux a while ago (easy since it was mostly straight C, with some Starbase for rendering). In contrast to the hours it took the c.1990 "Big Iron" to render a plate, even my pokey little kitchen computer (800MHz Celeron) can blow through a 1280x1024 render in 20 seconds.
Emboldened by the speed of rendering, I ran this huge, 10K by 10K pixel rendering (30 minutes on the Celeron):