[SOLVED] Motherboard is hotter than CPU in new build.

Jun 2, 2020
PC 1 :
MOBO -> MSI B450M Pro VDH Max - 48 C
CPU -> AMD Ryzen 5 3400G - 40 C
16GB RAM. 512GB SSD. Stock Cooler. Just one exhaust fan.

PC 2 :
MOBO -> MSI A320M-A Pro Max - 40 C
CPU -> AMD Athlon 200GE - 39 C
8GB RAM. 256GB SSD. Stock Cooler. Just one exhaust fan.

New Build. The following temperature are in UEFI. Just power on the system. Why my motherboard in 1st PC became this hot compared to CPU while the Motherboard of the 2nd PC is same as the temp of the CPU? I ran the system idle for 30 minutes, the temperature stays there.


When you boot into bios/uefi screen, the cpu stays under @ 50% load, it won't 'idle' until power options are enabled in windows. There's a considerable difference between a 50% load on the 3400G and the Athlon 200GE, the 3400G is going to use significantly higher amounts of power. This affects everything to do with the power delivery circuits. There's absolutely no telling which of the temp sensors the motherboard is actually sampling on either board, where they are placed etc. If the temp sensor on the 3400G board happens to be anywhere near the pcie hub, Sata controller, VRM's, anything to do with power delivery or its cooling methods then it can and will read something funky, but not abnormal.

The VRM's can easily hit 50°C with a cpu at 40°C because the VRM's do not have a giant heatsink with a giant fan attached to it directly. As can the pcie hub on the other side of the mobo. Sata controller chip is all about storage use, at a now 50ish% load etc.

To put it bluntly, you are chasing rabbits...
A 48C temperature is not really a concern at all, and in any case, temperatures at idle are pretty meaningless, since the components will generally get significantly hotter than that under load. If temperatures of components under load are getting into the 80s or 90s, that might potentially be a concern, but definitely not the 40s.

As for why temperatures could be different, there are all sorts of possible reasons. You are running a processor with more cores at higher clock rates, more RAM, and so on, and the B450 board supports more features. Air from the fans could be moving differently over the board as well. However, I suspect that if running the exact same components on both of the boards under heavy load, the temperatures of the B450 board would likely remain lower, as that A320 board lacks any heatsink on the VRMs, and appears to have a smaller heatsink on the chipset as well.


Probably because the two motherboards are different. In each case, the maker has decided exactly what component is most important from the perspective of cooling needs, and what its "normal" temperature should be. THAT is where they have placed the temperature sensor on each board. THAT also is how they have decided what is the "proper" target temperature for that sensor in setting up their automatic SYS_FAN header cooling control system. There is no universal sampling point or temperature target for all motherboards.

Let me echo the advice from SkyNetRising. Get at least one more fan as an intake, MAYBE eve two intakes, to increase overall air flow thorough your case and thus remove heat faster.
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