My printer has a perfectly ordinary 8-bit ATmega board, the same one a thousand machines ship with, and for years I assumed that was simply the speed ceiling. Push the feed rate too high and the motion would stutter, corners would round off, and the whole thing felt like it was working hard to keep up. It was. An 8-bit micro doing all the trajectory maths in real time runs out of cycles long before the steppers run out of torque.
Klipper changes where that maths happens. The clever idea is to split the job: a Raspberry Pi does the heavy trajectory and look-ahead planning, then sends precisely-timed step commands down to the microcontroller, which becomes a dumb but very accurate metronome. The Pi has cycles to spare. The result is that the same hardware suddenly moves faster and smoother, because the bottleneck was never the motors.
Flashing it is the only fiddly bit. You build the firmware for your specific MCU, flash it over USB, then the Pi talks to it. The configuration lives in a single readable printer.cfg, which after years of recompiling Marlin to change one number felt like a holiday.
[printer]
kinematics: cartesian
max_velocity: 300
max_accel: 3000
max_z_velocity: 5
max_z_accel: 100
[stepper_x]
step_pin: PF0
dir_pin: PF1
microsteps: 16
rotation_distance: 40
Want to change acceleration? Edit the file, type RESTART in the console, done. No toolchain, no reflash, no twenty-minute compile to discover you got a pin name wrong.
The honest results: I roughly doubled my usual print speed with better surface quality, not worse, because the pressure advance and proper look-ahead clean up the corners that high speed used to ruin. There's a calibration evening involved, and you have to actually read the docs, which are excellent. But the payoff is a printer that feels like a different, much more expensive machine, sitting on top of the cheap board I already owned. That's my favourite kind of upgrade.