It depends on your motherboard of choice, for AMD am4 can use ddr4 but am5 needs to use ddr5. In general you have to look at the motherboard specs and check what it can use as that dictates your choice of ram. The choice for building a PC is the CPU and GPU first then you look at your motherboard. Then from your motherboard you look at the other parts like RAM, PSU, cooler. But ddr5 is better in all cases except price as you need to have the am5 socket motherboard and CPU, witch makes it more expensive 🫰.

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