ConclusionWe 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. Actually, I'm impressed with how well this two-generation-old platform can run the newest processor—thank you, AMD. Intel would have definitely charged us for a new chipset—twice.
Using the latest BIOS update, which adds Ryzen 3000 processor compatibility, setup was a breeze, no major issues to report. All AMD BIOSes use a software component called "AGESA", which is provided by AMD to the motherboard vendors. All the vendors have to do now is add their motherboard specific features and branding—the core software remains unchanged and is controlled by AMD. This not only takes tremendous work off the motherboard vendors, it also enables AMD to centrally design, develop, test, and release updates. Such an approach not only improves software quality, it also pushes new capability to all motherboards without the motherboard vendor having to get involved, which is almost magical.
We were surprised to see the full range of overclocking, tuning, and tweaking options appear in this old motherboard's BIOS. This also goes for memory support. With the memory controller located inside the processor and AMD's AGESA providing the framework for memory settings, initialization, training, and compatibility, many memory modules that previously had issues will run infinitely better now. Can I use the word "magical" again?
Not everything is peachy, of course, as high-end motherboards are expensive for a reason. They come with seriously overbuilt VRMs, which work more efficiently and spread the heat generated during voltage conversion out over a wider area by using more components. These motherboards also include more premium heatsinks to transport the heat away. We took a closer look at VRM temperatures and were shocked that they can reach up to 140°C when B350 is paired with a powerful processor. This sounds bad at first, but the solution is: don't use watercooling.
While this might sound counterintuitive at first, it actually makes sense when you consider that an air cooler will generate some airflow around the processor's socket area, which isn't the case with watercooling. Of course, this can be mitigated with case fans, too. All we did was switch from water to air, and VRM temperatures dropped by 30°C. While they're still not nice and cool with around 110°C, they're now at a level these components are designed to withstand. It's also worth mentioning that most of the heat isn't coming from the MOSFETs themselves, but the chokes nearby. These chokes are really just metal coils in a package without any logic inside, so they are fine to get hot.
Now, the big question: should you buy a B350 motherboard for Ryzen 3000? I think it depends. If you plan on using a weaker CPU like the Ryzen 5 3600, then by all means go for it. If you want to power more powerful processors definitely keep an eye on VRM temperatures and ensure there's some airflow around them. You could probably also give the Ryzen 7 3700X a go since it has a TDP of just 65 W and beats the Core i9-9900K in various multi-threaded tests. If you insist on the 3900X, we recommend you at least pony up a few more dollars toward one of the better motherboards based on this chipset, such as the Gaming Pro Carbon series from MSI or Aorus Gaming 3 series by GIGABYTE, which offer X470-type CPU VRM solutions on motherboards priced around the $110-mark. You can pair such boards with a 3900X for endless number crunching.
Another aspect of choosing the B350, or indeed any older motherboard, to go with your 3900X is that you lose out on PCI-Express gen 4.0. For the current graphics card scenario, this is irrelevant, but the lack of PCIe gen 4.0 limits your M.2 NVMe SSD upgrade path if your work environment demands fast local storage. Major SSD manufacturers already announced PCIe gen 4.0 SSDs capable of utilizing that bandwidth for transfer rates as high as 5,000 MB/s. Besides PCIe, some of the newer motherboards offer modern connectivity, such as USB 3.1 gen 2 ports, 2.5 or 10 GbE wired LAN, 802.11ax WLAN, etc., which may not be useful to you anyway.
Given how expensive X570 motherboards are, such an approach can free up cash for you to spend on a more powerful processor, better graphics card, or more memory. This makes even more sense when money is tight. It also provides a nice upgrade path if you are already on a Ryzen platform, possibly already using a B350 motherboard. Not having to purchase a new motherboard, especially at launch-day pricing, is always a good option, and it'll let you grab a Ryzen 3000 CPU immediately and look at motherboard choices later. We also tested Ryzen 3000 on X470 on launch day and saw excellent results for that combo, too.
What's also important is that "just gaming" won't stress your VRMs anywhere close to what highly threaded rendering or scientific applications will do. Even in the thermally constrained water-cooled scenario, we couldn't record any performance differences in gaming or light apps. Even with our high-end RTX 2080 Ti graphics card, we didn't notice any gaming performance difference between the B350 and X570.
AMD has done a commendable job in enabling people to save money by opting for older-generation motherboards to go with their latest processors. The AMD X570 is an expensive platform, but provides bleeding-edge connectivity. The only compelling argument for those buying a 500-series chipset motherboard is the M.2 NVMe SSD upgrade path. Perhaps when AMD releases the successor to B450, reportedly in 2020, can you have affordable motherboards with at least one M.2 slot that has PCIe gen 4.0 wiring. Until then, have at it with the B350; AMD wants you to be happy.