Built a small machine using an Asrock N100DC-ITX motherboard, it has an Intel N100 built in and I also have 1x NVMe and 2x HDDs. The board has a DC Jack so no external PSU.
First time I booted it, the NVMe had Opensuse on it so I played around a little, no problem. When I boot into BIOS also no problem.
When I boot into Unraid, there is a strange sound coming from the back of the board, sounds like an interference sound. I cannot tell if it's coming from the ethernet port or from the power DC Jack. I think it's from the power.
I recorded it with my phone and bumped the sound +20 dB, this is how it sounds like. You can hear the fans and that sound. https://soundcloud.com/user-300866676-719653331/n100-1
https://soundcloud.com/user-300866676-719653331/n1002
For power I tried using both an Intel NUC 65w power adapter and an Asus laptop 90w power adapter, the one Asrock recommends on their website. The system has been running for 1-2days, with 4 containers and Home Assistant VM, it idles at around 16w. Without Home Assistant, it drops to 11w.
Any idea what that sound is?
Edit 1: If I go into BIOS and turn off Intel Turbo Boost Technology then it is silent but also kills my performance?
Edit 2 So because I did not want to leave Turbo Boost on, I did some more digging and also realized my CPU was always boosting in Unraid. using "watch grep "cpu MHz" /proc/cpuinfo" it was almost always between 2900Mhz and 3300Mhz. I installed Tip and Tweaks plugin and set Normal CPU Scaling Governor to power saver. The sound is gone and now it seems the CPU goes all the way down to 600 MHz and up to 3400MHz depending if it needs it. I don't know if the power saver will affect performance in any way but so far so good and I don't have hear that wheeeeee anymore.
When I first started building the machine, I only had the NVMe in the board, the HDDs came at a later date. The sound was still present.