Over the past week we've been testing the VRM on a number of entry-level AMD B550 motherboards such as the Gigabyte B550M DS3H, Asus Prime B550M-A, Asrock B550M Pro4, and the MSI B550M Pro-VDH Wi-Fi. While we have yet to completely wrap up that testing, so far we've been able to gather some pretty interesting results.

We've already looked at how some of the more expensive B550 boards compare to the MSI B450 Tomahawk, so we thought it might be interesting and perhaps more relevant to see how the MSI B550M Pro-VDH Wi-Fi stacks up, as well as the B550-A Pro. We also realized we've never looked at any B350 boards since our formal VRM thermal testing began after the release of the B450 chipset.

On hand we have the MSI B350 Tomahawk, so we'll be adding that to the mix and it will be an excellent reference point for the B450 and B550 Tomahawk boards.

Something we need to discuss before getting into the test results is pricing, and of course, the VRM configuration for each board. The original B350 Tomahawk started life at $100 and featured a very basic VRM, the 4-phase vcore used Niko PK616BA MOSFETs on the high-side with a pair of Niko PK632BA MOSFETs on the low-side with a single inductor per phase.

The MSI B450 Tomahawk was slightly higher at $110, but you were getting a much better motherboard in terms of VRM performance. We're still looking at a 4-phase vcore but this time upgraded to a pair of On Semi 4C029N FETs on the high side with a pair of On Semi 4C024N Fets on the low-side, though each phase still only feeds into a single inductor.

Now, the latest B-series Tomahawk board, the B550 commands a $180 price tag and that's obviously a huge step up. However, if we look at the VRM, this board is in a completely different league, too. The 5-phase vcore sees each phase driven by a pair of ISL99360 60A powerstages into a pair of inductors, so that means there's ten 60A powerstages in total, just two less than that of the X570 Tomahawk.

Therefore there's no comparing the B450 and B550 versions of the Tomahawk, they might share the same name but they're radically different in terms of quality. That's great and all, it's certainly nice to have the option of higher quality motherboards, but what we also wanted to learn is how do the more affordable MSI B550 boards compare to the much loved B450 Tomahawk?

The MSI B550M Pro-VDH WiFi costs $15 more than the B450 Tomahawk at $125 and you get PCI Express 4.0, front panel USB Type-C and Wi-Fi support. The Pro-VDH essentially copies its VRM from the B450 Tomahawk, there's a slight difference in the controller revision used, but that shouldn't change anything. The heatsink has also changed, but still looks quite good.

Then the B550-A Pro comes in at $140 making it $30 more expensive than the B450 Tomahawk. The B550-A Pro is a significant upgrade offering a 10-phase vcore VRM. From the IR35201 controller MSI takes 5 signals, each of which is then doubled using an IR3598 phase doubler. Each of the 10-phases is driven by an On Semi 4C029N FET on the high-side with an On Semi 4C024N Fet on the low-side. These are the same MOSFETs used by the B450 Tomahawk and B550M Pro-VDH WiFi, there's just two more sets of them and each phase feeds into its own dedicated inductor. So in terms of thermal performance the B550-A Pro should have a big advantage over those boards.

Test Setup and Configurations

For this test and all future AM4 VRM thermal testing we've built a dedicated system with the help of Corsair who sent over their Obsidian Series 500D mid-tower case, RM850x power supply, iCUE H150i RGB Pro XT all-in-one liquid cooler and 32GB of Vengeance RGB Pro DDR4-3200 memory. This is the same configuration we recently to test Intel Z490 motherboards.

The Obsidian 500D has been configured with a single rear 120mm exhaust fan and two top mounted 140mm exhaust fans. Then in the front of the case is the H150i 360mm radiator with three 120mm intake fans. This is a pretty standard configuration, air-flow is good, and in a 21 degree room we'd say this is an optimal setup.

For recording temperatures we're using a digital thermometer with K-Type thermocouples and we'll be reporting the peak rear PCB temperature. Finally we're not reporting Delta T over Ambient, instead we maintain a room temperature of 21 degrees and ensure a consistent ambient temperature with a thermocouple positioned next to the test system.

We've got four configurations using three different Ryzen processors. The base configuration which every board will pass with ease sees us use the Ryzen 7 3700X, a low powered part that only draws around 85 - 90 watts in our Blender stress test. This should provide a baseline reference.

Then we have the Ryzen 9 3900X which will be tested completely stock, with no overclocking and no changes made to the BIOS other than loading XMP. The 3900X configuration pushes CPU load up to around 140 watts in our test. Then we have the Ryzen 9 3950X which has been tested twice, one stock and then with a 4.3 GHz overclock using 1.375v. The stock config only pushes CPU usage to around 140 watts, but it does so at a lower stock voltage, so we're pulling slightly more amperage which will cause a little more strain on the motherboards VRM.

Finally, the 4.3 GHz configuration pushes CPU power consumption right up to 200 watts, so this is our most extreme test.


First, here's a look at the MSI Tomahawk boards without the B550M Pro-VDH WiFi and B550-A Pro included. With the Ryzen 7 3700X installed the B350 Tomahawk peaked at 61C which is quite warm given the CPU used. The B450 Tomahawk reduced that temperature by 12 degrees to 49C and the latest model, the B550 Tomahawk reduced the peak temperature to just 38C.

For reference the X570 Tomahawk peaked at 40C, a few degrees higher than the new B550 model and while it's true the X570 has a better VRM, it's only better at higher loads and is less efficient when paired with lower end parts like the 3700X. Still we're looking at very similar results between the B550 and X570 Tomahawk boards, so that's a great result.

Out of interest we included the MSI X570 Gaming Pro Carbon which we've called one the worst X570 motherboards in terms of VRM quality. 56C is a horrible result for a $300 X570 board, that's only 5C better than the old B350 Tomahawk.

Stepping up to the Ryzen 9 3900X changes things considerably, not only is the B350 Tomahawk peaking at just over 100C, but the difference between it and the B450 version is greater. The B450 model peaked at 71C which is a great result and an 11C improvement over the X570 Gaming Pro Carbon.

The B550 Tomahawk is even more impressive. Whereas the B450 model saw a 22 degree rise in temperature from the 3700X configuration, the B550 model increased by just 7 degrees and was 2C cooler than the X570 Tomahawk.

Now with the Ryzen 9 3950X installed, the B550 Tomahawk VRM temp increased by just 4C and the B450 model saw an 8C increase. Interestingly, the B350 Tomahawk saw a small increase and as far as we could tell, it was able to avoid throttling the CPU in our hour-long stress test.

In our most extreme stress test, the 3950X was overclocked to 4.3 GHz using 1.375v. The B350 Tomahawk failed this test which was not all that surprising as it began intermittently throttling the 3950X down to 500 MHz for a breather, before cranking it back up, only to repeat the process moments later. By the end of the hour we ended up with an average clock frequency of 3889 MHz. The board survived 11 minutes before it began to throttle.

The X570 Gaming Pro Carbon also failed this test, but it took just 4 minutes to hit its thermal threshold and as a result ended up with an average operating frequency of just 3426 MHz, a dismal result for an expensive X570 motherboard.

Impressively the B450 Tomahawk passed this test, peaking at 91C, though it was difficult to stop the voltage drop on this board and by the end of the test HWinfo was reporting an average voltage of 1.320v. Hard to say how accurate that is, but we wouldn't be surprised if it were completely accurate.

The B550 Tomahawk performed very well, running just 3C hotter than the X570 model and that saw it peak at just 62C, an incredible result really.

Adding the MSI B550M Pro-VDH WiFi and MSI B550-A Pro to the results, we'll focus on these motherboards. With the 3700X both boards performed well enough and here we're looking at B450 Tomahawk-like performance. Embarrassingly, both beat the X570 Gaming Pro Carbon as well.

Stepping up to the Ryzen 9 3900X once again reveals some interesting data. Here the Pro-VDH matches the B450 Tomahawk exactly, while the B550-A Pro was a tad better, dropping the VRM operating temperature by a significant 16C, making it just 10C hotter than the B550 Tomahawk. Again, both B550 boards were better than the X570 Gaming Pro Carbon.

With the Ryzen 9 3950X installed the Pro-VDH ran 3C cooler than the B450 Tomahawk, while the B550-A Pro was 21C cooler. Impressive results for both, but particularly for the B550-A Pro.

Testing with the 3950X overclocked had the Pro-VDH running quite a bit hotter than the B450 Tomahawk, though this might be an unfair comparison as the B550 board didn't suffer quite the same degree of voltage drop, so in reality they might be much the same. Either way the B550 Pro-VDH did pass this test, no throttling or crashing.

The B550-A Pro was once again very impressive, peaking at just 76C and that means you can throw anything at this board without having to worry about the VRM.

What We Learned

That's how the entry-level MSI B550 boards compare with past B450 and B350 Tomahawk motherboards. In a way you could say the MSI B550 Pro-VDH WiFi is the new B450 Tomahawk, it barely costs more and uses the MicroATX form factor. The VRM is basically identical and the cooling is good for a budget board.

The smaller form factor does mean you're missing out on the secondary PCIe x16 slot, though it was only wired for x4 bandwidth on the B450 board, and one of the PCIe x1 slots is missing as well. The new B550 board also only offers four SATA ports instead of six, but in their place is a second M.2 slot which may be preferable.

The benefits of the MSI B550 Pro-VDH WiFi include the Intel Wireless-AC 3168 with Bluetooth 4.2, PCIe Gen4 for the primary PCIe x16 and M.2 x4 slot and USB 3.2 support with many more high speed ports. So if you're interested in PCIe 4.0 support for a high speed storage device, better USB performance, and of course WiFi/Bluetooth support out of the box, then paying $15 more for the Pro-VDH WiFi seems like a good deal to me.

As for the MSI B550A-Pro, it's a ~$30 premium compared to the B450 Tomahawk but in terms of quality and design it's a significant upgrade. The VRM quality is substantially better, as are the heatsinks cooling it. As for other features, you get PCI Express 4.0, an extra M.2 slot and far better USB support, this time including two USB 3.2 gen 2 ports for 10 Gbps transfer seeds.

Not everyone is happy about the price increase in the line-up, but at the same time it's fair to recognize the boards are technically better. On top of that, we're seeing big demand for B550 products and less supply due to the global pandemic, which means somewhat sketchy availability and less chances of grabbing a great deal beyond the MSRP.

All we can say for sure is, you're now getting better quality AM4 boards with better features so the marginal increase in pricing isn't for nothing as we've seen many claim. You can expect a full roundup of the best B550 motherboards in the next few weeks, so stay tuned for that.

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