Where did you see this? I have an x370 I'd love to run an 5k on.It seem that on cheap b350, a 3900x work on many application exactly like on an expensive x570:
On aircooling it seem to be about the same for anything.
We were curious to see how well a cheap B350 motherboard could run the latest and greatest 12-core, 24-thread Ryzen 9 3900X and were pleasantly surprised that there was no smoke, or sparks flying — it just works.
That said there is talk of the new 5xxx cpu working on the 3xx series MB, maybe that is worth to take a look for your specific motherboard.
https://hothardware.com/news/amd-300-series-motherboards-with-ryzen-5000-cpuWhere did you see this? I have an x370 I'd love to run an 5k on.
Nice I have a B450https://hothardware.com/news/amd-300-series-motherboards-with-ryzen-5000-cpu
AMD Ryzen 5000 CPUs Allegedly Can Run On Aging A320 And X370 Motherboards
AMD Ryzen 5000 Zen 3 Desktop CPUs Reportedly Running on A320 & X370 Motherboards, B450 Support Already Added By ASUS & Gigabyte