B450 vs B550 Motherboards
Both are mid-range AM4 chipsets and both can run a Ryzen 5000 processor. B550 is the newer one, and what it adds is PCIe 4.0 for the graphics slot and the first M.2 drive, where B450 is PCIe 3.0 throughout. B550 boards are also newer designs, so they more often carry stronger power delivery, 2.5 gigabit networking and Wi-Fi 6. In exchange, B550 dropped support for the oldest Ryzen chips, which only matters if you are reusing one.
Buying new for a Ryzen 5000 build, B550 is the safer choice: it works with those processors out of the box more often and gives the drive and graphics card a PCIe 4.0 connection. B450 still makes sense when it is clearly cheaper and you are pairing it with a modest processor and a PCIe 3.0 drive.
What you give up, in numbers
How the two sizes actually differ once you look at every board on sale, rather than at what the standard permits. Measured across 28 B450 and 62 B550 boards at the retailers we track (27 and 61 in stock today), and updated daily.
The picks on each side
The cheapest board on each side, and the cheapest one that clears a floor worth clearing: enough power headroom for the socket’s top processor, and Wi-Fi 6E or better. Recalculated daily from live prices.
B450
Best all-round
No board in stock clears both the power and Wi-Fi floor.
B550
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Common questions
Does B450 support Ryzen 5000?
Yes, with a BIOS update. Many B450 boards were made before those processors existed, so check the board's support list and BIOS version, or choose a board with a BIOS flashback button.
Is B550 worth it over B450?
Usually, when the price gap is small. You get PCIe 4.0 for the graphics slot and the first M.2 drive, and typically a more recent board design. If the B450 board is much cheaper, the practical difference in games is small.
Which processors does B550 not support?
B550 does not support Ryzen 1000 and 2000 series processors or the Ryzen 3000G series chips with integrated graphics. It supports Ryzen 3000 processors without integrated graphics, and the 4000G, 5000 and 5000G series.
Does PCIe 3.0 on B450 slow down a graphics card?
Very little with a card that uses all sixteen lanes. Cards wired for only eight or four lanes lose more on PCIe 3.0, so check how many lanes a budget card uses before pairing it with a B450 board.
Keep going
Browse every B450 board or B550 board with filters, put two specific boards head to head, or read up on choosing a case to fit the board you pick.