The plotter I built way back in high school

It all started 1986 with these stepper motors and interface that my older brother Markus built. He even suggested I build a plotter.

I then started to write software to drive the motors trough the C64's user port. To get the step timing accurately enough, I had to use assembly language to generate the pulses. I ran the assembly language off an interrupt, which I had going off at my 'step rate'. Main line code, which was a mix of assembly language and BASIC, filled a buffer with step instructions, while the assembly language read it out in the background. The slowness of the BASIC components thus were non critical, as plotting was able to continue as BASIC was doing other things. In the process, I learned a principle which is rarely violated on projects though: The software always takes way more effort to develop than the hardware.