I'm using a be quiet! Pure Loop 360 AIO with the radiator mounted at the top, a SATA-powered Coolmoon ARGB/PWM hub, and three case fans connected through a separate motherboard header. The pump is connected to the AIO_PUMP header, but the three radiator fans are connected to the Coolmoon hub.
The radiator fans spin normally, but the motherboard never detects an RPM signal from the hub. Every boot shows a "CPU Fan speed detection error," and the CPU_FAN header appears as N/A in BIOS. I disabled the warning so the system would boot, but I'm unsure whether that is safe or whether the fans could stop or fail to ramp up unexpectedly.
The system uses a Ryzen 7 9800X3D on an ASUS TUF Gaming X870-Plus WiFi. Temperatures are about 47°C at idle and 55–65°C while gaming. After a 10-minute Cinebench multi-core run, the CPU reached 96°C at roughly 145 W package power.
Is this mainly because the inexpensive hub does not pass through a tach/RPM signal? Should I use a splitter or a better hub, and is it safe to keep running with the BIOS warning disabled?
3 Answers
Your board has multiple CPU and chassis-fan headers, so the hub is not really necessary here. A simple PWM splitter or extension cable would be a better workaround. Put one radiator fan on CPU_FAN so the BIOS receives a valid tach signal, then connect the other radiator fans through the splitter or another controllable header. You can also set the CPU_FAN monitoring threshold lower temporarily, but that only hides the symptom rather than fixing the missing RPM signal.
The fans spinning means they have power, but it does not prove that the motherboard can monitor their speed. With the current setup, the BIOS warning is about missing tach feedback rather than necessarily indicating that the fans are stopped. Still, it is better not to leave the warning disabled permanently. The Cinebench temperature is near the processor’s normal thermal limit, so verify that the pump is running at full speed, the radiator fans respond to temperature, and the AIO is mounted correctly before relying on the system for heavy workloads.
The CPU cooling fans should normally be connected to the motherboard’s CPU_FAN header, while the pump stays on AIO_PUMP. Many inexpensive hubs distribute PWM power but do not send one fan’s tach signal back to the motherboard, which explains the N/A reading and boot warning. Use a proper PWM splitter, connect one radiator fan directly to CPU_FAN, or use a hub that explicitly supports RPM/tach pass-through. Make sure the splitter or hub is SATA-powered if needed, since a motherboard header should not be overloaded.
The pump is already on AIO_PUMP. I used the hub because one radiator-fan cable is too short to reach CPU_FAN or CPU_OPT, but I’ll replace it with a splitter or connect at least one fan directly to CPU_FAN.