ATXflip is an adapter board to use old AT motherboards in modern ATX cases with modern and safe ATX power supply units. The power switch of the case is connected to the board and the microcontroller takes care of controlling the power supply and activating the turbo mode on old boards.
The software was written in AVR-C and can (as always) be found on GitHub: https://github.com/Manawyrm/ATXflip/tree/master/src
The first revision of the hardware was wired on a perfboard:
Later a PCB was produced:
The project was shown in the RetroNews by PhilsComputerLab.