What motherboard suits Ryzen 9 3900XT, and how should power delivery, memory, and ports be balanced?

  The 3900XT runs AM4 with DDR4. A B550 handles one GPU and ordinary M.2 storage; X570 matters only for heavy PCIe 4.0 devices or a workstation setup.

  For long 24-thread compile or render sessions, pick a board with proper VRM cooling and power headroom; a gaming build doesn't need a flagship chipset. Decide the rest on USB, networking, and expansion slots.