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Increasing memory speed causes Corsair AX1600i fan to ramp up with certain TRX40 boards

I’m experiencing a strange issue with some TRX40 motherboards with a Corsair AX1600i power supply when I increase the memory frequency. If I use a motherboard with the XDPE132G5C controller and 16 phase power delivery (I’ve tried an Aorus TRX40 Xtreme and an MSI Creator TRX40) and increase the memory speed from 2133, it causes the PSU fan to run. The AX1600i is a monster, capable of running fanless up to 800W. I also have a Zenith II Extreme Alpha. With the Asus board, the 0 RPM mode of the AX1600i functions properly when running the memory at XMP (3600MHz 16-19-19-39, 1.35V). I was able to apply 600W of load to the power supply and the fan never came on, with the PSU temperature topping out at about 39 degC. With the Aorus TRX40 Xtreme, as soon as the XMP settings are applied, the fan comes on and runs at around 460 RPM. If I apply the same 600W load using the Aorus board, the fan ramps up to around 800 RPM. As long as I run the memory at 2133MHz, the fan behaves normally. I’ve played around with other settings in the BIOS and it seems to be the memory frequency specifically that makes the fan spin up. Increasing the memory voltage doesn’t make the fan spin up.

I really like the lane allocation of the TRX40 Xtreme vs. the Asus Alpha, since it doesn’t disable this if you use that like Asus board does, but the first priority of my build is for it to be as quiet as possible. There’s really no reason for the fan to be running on the AX1600i with the Aorus board. I’m thinking there has to be something I can change in the BIOS to keep the fan from running, but I can’t think of anything. Could it be the difference in power delivery design that is causing this? The Aorus board actually draws a little less power than the Alpha, so I don’t understand why the fan is spinning up. Even during idle with the PSU temperature less than 30 degC and power draw less than 250W the fan is running. The temperatures and load values were taken from Corsair Link 4.

Any help with or explanation for this would be greatly appreciated.

I got an explanation for the difference in fan behavior between the two boards from the one and only jonnyguru. For reasons I can’t determine, the Aorus board is drawing a lot more power on the 5V rail. This is causing the fan to kick on to cool the mosfets in the power supply. I don’t know what to change in the BIOS to lower the amount of current being used on the 5V rail. I removed 4 sticks on memory and dropped the frequency from 3600 to 3200, and while it did slow the fan down a little, the Aorus board is still drawing a lot more power on the 5V rail than the Asus board.

The thread on the Corsair forum is linked below.
https://forum.corsair.com/v3/showthread.php?t=201428