The Original Prusa MK4 is equipped with two proprietary boards: the xBuddy and the LoveBoard. The two are connected by a main cable. When replacing a part in the extruder, you will be able to do so directly on the extruder, without needing to open the extruder cable bundle or the main board.
Each connector has a label near it showing the component attached there.
This connector breakout board connects all the extruder cables. In order to access the LoveBoard, slide up the cover, and unscrew the love board cover right.
The xBuddy is a 32-bit board, with Trinamic drivers for silent motor operation and Wi-Fi/LAN connection.