Question: what is fclk frequency ryzen?
Answer: It stands for Infinity Fabric Clock according to AMD. The FCLK is used for memory (RAM), by default it will be the same clock speed to your RAM (1800MHz FCLK : 1800MHz clock speed). But, FCLK can be tweaked. If you use the X570 motherboard, then it's tweakable, but no 400-series motherboard will support FCLK tweak.