Seasonic M12D 850W: DC-to-DC Perfection?

Temperatures, Fan Speed, and Acoustics

The temperature results of the Seasonic M12D are another area where it excels, surpassing most other power supplies. When you compare the temperatures to the increasing speed of the fan, you can clearly see how well the design works. Many other power supplies ramp up fan speed even when it's not necessary, and frequently higher fan speeds and increased airflow barely manage to keep temperatures in check. In contrast, the M12D stays under 50°C at all times; there's a jump in temperature on the secondary heatsink between 20% and 50% load, but it's not enough to actually require a significant increase in fan speed. Once the fan does begin to speed up, however, we immediately see temperatures begin to fall off, showing that the heatsinks are working exceptionally well.

With loads of up to 50%, power output generally stays below 400W and this power supply is virtually silent. Only beyond 50% load is the fan begin to kick in, and as we saw above it does a good job at keeping temperatures in check, reaching a maximum 2300RPM. Seasonic is a bit conservative at higher loads, since the temperatures are still more than reasonable, but they are proud of the engineering that has gone into this design.

At maximum loads and fan speeds of 2300 RPM, it's no surprise that noise levels aren't great. Maximum acoustic noise reaches 31dB(A), which you can definitely hear -- although as usual, creating a load of 850W generally means a lot of noisy graphics card and CPU fans as well. Seasonic prefers to take a conservative approach and avoid overheating, which is good for end-users and component longevity. Given that few users will put such a heavy load on their PSU, however, noise levels of only 17dB(A) at up to 400W are practically undetectable -- it's definitely at the lower boundary of what our equipment can measure. There is however a small ticking noise that can be heard from the heavily undervolted fan, which is common with fans that used normal voltage regulation instead of a PWM controller. (Antec has the patent for PWM controllers in PSUs.)