Toms Hardware published AMDs AM5 Will Launch With Only DDR5 Support for Ryzen 7000, Dual-Chipset Design
A quote from the article:
Our sources have confirmed that AMD's AM5 platform for the 5nm Ryzen 7000 'Raphael' CPUs will only support DDR5 at launch.AMDs AM5 Will Launch With Only DDR5 Support for Ryzen 7000, Dual-Chipset Design