While Klipper is referred to as firmware and treated as a direct alternative to Marlin, the reality is a little more involved. ... To do this, Klipper firmware (written in C) is installed on your printer's controller board (or boards), which is then connected to the Raspberry Pi by USB.

Why should I use Klipper?

Klipper was made to lower the effect of this processing time and improve printing performance by offloading tasks to another device. Klipper utilizes the extra computing power to essentially make a pre-developed plan for G-code commands, so your printer only needs to carry out the commands, not process them.

Does RepRap use Marlin?

Marlin is firmware for RepRap single-processor electronics, supporting RAMPS, RAMBo, Ultimaker, BQ, and several other Arduino-based 3D printers. It supports printing over USB or from SD cards with folders, and uses lookahead trajectory planning. Marlin is licensed under the GNU GPL v3 or later.