VRM Overview

The VRMs are usually an area of a lot of variation between Mini-ITX motherboard designs, and it's no different here. It's a fairly standard 10+1+1+1 power phase delivery and being B860, there's no need to factor in overclocking and it's extra demands. But the cooling arrangement is a lot more elaborate than a casual glance might suggest. Two large thermal pads connect the rear heatsink to back of the VRM areas and then top side we have two VRM heatsinks that are linked via a heatpipe. There was very little mention of a VRM fan being involved other than a single small diagram in on the product overview page on ASRock's website, but the additional clue was something called a PWM fan in the BIOS and software fan control.


The fan exhausts air through the I/O shroud heatsink towards the CPU socket through small vents. As you can see above, by default it sits at 20% speed, gradually rising to 70% when the motherboard temperature (which seems to be different to VRM temperature, at least according to HWiNFO that listed both motherboard and MOS readings), and hitting 100% at 70°C. Now, many Mini-ITX enjoyers will have nightmares about noisy chipset fans (ASUS ROG Strix X570-I Gaming owners, we hear you), but thankfully the fan remained inaudible throughout our testing and is completely configurable in the EFI too. If you want to make sure it stays that way, setting the speed to a maximum of 50% did the trick, but you may want to keep an eye on temperatures.


The actual VRM peak temperature reached 58°C using our data logger, while HWiNFO came in a little higher at 62°C. This was using a Core Ultra 9 285K, so the worst case scenario, and while we've seen cooler, it's more than acceptable given overclocking isn't on the cards.


The 10 vCore phases are dealt with by Renesas R2209004 110 A smart power stages, which are the same, albeit fewer, as MSI's MPG X870E Carbon Wi-Fi as well as the ASRock Phantom Gaming B860I Lightning Wi-Fi's B850 sister board.


The rest of the phases are via 45 A Vishay SiC450 and 75 A Renesas RAA220075R0 MOSFETs, ASRock has opted for a Renesas RAA229134 PWM controller.