I have a b550 f gaming motherboard and a ryzen 7 5800x which I thought supported 4000 MHz but it doesn't let me change it. The minimum it will let me change it to is 2666 MHz and I don't understand why.
What BIOS version are you working with on the motherboard? You might want to manually input the timings, frequency and voltages into BIOS and see if that works out. Your first task is to make sure you're on the latest BIOS prior to tinkering with ram.
I have a b550 f gaming motherboard and a ryzen 7 5800x which I thought supported 4000 MHz but it doesn't let me change it. The minimum it will let me change it to is 2666 MHz and I don't understand why.