Power Consumption and Temperatures

The ASUS ROG Crosshair VIII Extreme uses a single, large heatsink for the VRM which is capable of cooling all the power stages with ease. A back-panel is also a part of the cooling solution. Even though it is minor, pads are placed on the rear of the VRM section for additional thermal dissipation through the PCB.

VRM Voltage Probe

Using a multimeter probe, I measured the voltage on the back of the coil under load. This measuring point is after the 12 V step-down occurs. With a fixed voltage of 1.4 V for the Vcore and 1.15 V for the SoC, I took the measurements during load and proceeded with this process for each LLC the BIOS offers for selection. A second readout has been taken from the software readout, listed as SV12. This value is measured by the CPU as the current voltage input.


For temperature measurement, I use a Reed SD-947 4 channel Data Logging Thermometer paired with four Omega Engineering SA1 Self Adhesive Thermocouple probes. One probe directly touches the chipset and two are placed on select power stages. The last probe actively logs the ambient temperature.

For the ASUS ROG Crosshair VIII Extreme, one probe is placed along each bank of power stages. A probe is left out to log the ambient temperature. All temperatures are presented as Delta-T normalized to 20 °C, which is the measured temperature minus the ambient temperature plus 20 °C. The end result accounts for variation in ambient temperature, including changes over the course of a test, while presenting the data as if the ambient were a steady 20 °C for easy presentation. Additionally, there is direct airflow over the VRM for the first five minutes, after which the fan is removed. This gives an idea of what to expect with and without moderate case airflow.

Prime95's Small FFT is used for maximum power consumption over a 30 minute period. For testing, I used a Ryzen 9 3900X set to 3.8 GHz and locked at 1.4 V, and 1.15 V for the SoC. Temperatures are logged every second, and the two probes are then averaged for a cleaner presentation before subtracting the ambient to calculate the Delta-T. The results are charted below.


The ASUS ROG Crosshair VIII Extreme fairs exceptionally well in the VRM torture test. I am confident that this motherboard can be used long-term with a heavy CPU overclock and minimal airflow. The Prime95 test is designed around the worst-case scenario for every situation.