well afaik, the 450 motherboards wont have support for ryzen 3(5000 series) until next year, earliest q1. and you will have to do a BIOS update as it wont work out of the box and the same goes for the b550s and x570s. SOME motherboard allows you to flash BIOS even without a processor, some don't. As you're buying a 450, can i assume that you are more after price to performance? in which case Zen 2(3000 series) is better in this regards. ALso you're local microcenter might be able to help you flash bios if you can't do it with out a cpu, though im not sure if the mobo has to be bough in micro center or not or if it costs money.
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