Buy a power meter, otherwise you can't see what or if any changes in the BIOS/OS have an effect on the power consumption and in the end on how to lower the temperature of the machine. Then try to tune the various aspects - P1/P2 levels, C-states, p-states, CPU governor, tunables on Linux/FreeBSD,...
This forum needs a wiki. I have seen good tips for that here, but they get buried deep under so many replies.
Besides that, what did you expect? You have chosen a pretty small case with small heat exchange fins, passive cooled. This thing will run hot, no matter of the tunings to lower the power consumption in idle mode. As soon as you really start using the CPU, it will run hot, and it also will stay at least really warm in idle mode. Your only chances to use it is to attach a fan on top of it.
You're right, after booting and idling, it gets around midle to high thirties Cº, after stressing the cpu (max 67º), it simply doesn't get lower than 45-46º. Got this one, because i had a non-used ddr4 stick. The rest of the n100 mini-pcs, either have embedded memory or use ddr5.
In the BIOS, I haven't found an option to change the speed of the RAM, so there is a high chance you need to test another module to see if it's identified in the correct way.
I tested with another stick, gskill 32GB 3200Mhz. Someone at the other thread, said that with a 32GB stick, it was needed to run it headless. Here it ran without problems. 3200 speed. At least on windows. I benchmarked, no crashes, no problems. Ironic, how the bios has the most esoteric settings, but misses the most vulgar ones, like voltage and timings.
Haven't tested the speed of the drive in my box. I don't care, it is fast enough for a firewall, and for a file server there is not enough space for hard drives. But based on the other findings (DDR4/DDR5 RAM, Intel vs. RT NICs) there might be a chance they just used 2 PCIe lanes and not 4 for the drive , which is strange, because just by saving two NICs (each takes one lane) this could be achieved.
Well, i do intend to run some VMs here. 1500MB/s is enough, but if they advertise x4 speeds, i want it. On this case, a ssd disk hardly fits, definitely not if it's attached to the cover. The supplied cable has a big plug. There is also a msata slot, so actually plenty of options here. 1 nvme, 1 ssd, 1 msata. Plus another one if adapting the wifi slot to ssd/nvme. Plus the usb ports.
Anyway, i might keep it instead of returning it. Performance wise, it's not bad. Passmark is around 6000, single thread is 2070. Pitty about the 2666Mhz memory. Maybe later i'll use that 32GB stick. I disabled intel's power management on Linux (intel_pstate=disable on grub), because there was always a core at full speed, even when idling.
EDIT: I installed rocky linux 9, temps are high because there is this kworker/0:0-kacpi_notify always on 20% cpu. Any ideas why this? kernel 6.3.2 from elrepo.
EDIT2: Ok, found which interrupt was causing issues and disabled it.
grep . -r /sys/firmware/acpi/interrupts/ |grep -v invalid to find which one (the one with a high number except gpe_all), and added
acpi_mask_gpe=0x6F to grub. Doing
echo mask > /sys/firmware/acpi/interrupts/gpe6F also fixes it.
