Hi,
I bought a N5105 from topton with a different motherboard than yours.
Motherboard is a GF-1338NP-12, V1.4 and software says it's a Techvision TVI7309X.
(It's the one that has a SERIAL port that "looks like a ethernet port".)
I also can't replicate the 2.8GHz with 12.53W CPU Package.
My MB/CPU runs AIDA FPU test (BIOS P1:15W,128s; P2:20W), with all 4 cores at 2.8GHz and the CPU package uses 17,19Watts.
I didn't replace the thermal paste yet, the max temp is 71C during the 128secs test at 2.8GHz.
Mains power measures 26.x Watts (2.8GHz full load) in the previous test and around 11 watts while idle in win10.
Box has 2x8GB RAM, 128GB SATA SSD, 256 NVMe SSD, keyboard, mouse, 1 eth port connected and HDMI monitor.
View attachment 25610
View attachment 25611
Interesting, here it says CPU VID is 1.112V while it was running the FPU test.
Could you see if you have a different CORE and VID voltages with CPU at 2.8GHz full load running aida FPU test?
View attachment 25612
-> Then after some minutes, it goes to this:
The 4 cores go to 2.6GHz with 14.9 W CPU package and 14.x W mains power consumption.
(So probably if I lock P2 to 15W, I'll get max 2.6GHz)
View attachment 25613
View attachment 25615
-> BIOS P1:15W,128s; P2:15W
From what I can see, each of the cores clock will fluctuate from 2.5GHz to 2.8GHz.
Bellow graph is for 10 minutes, looks like this would continue forever.
Mains power measures 24.x Watts.
View attachment 25617
View attachment 25618
Note: Don't mind the incorrect +5V value, I measured the SATA power cable and it's 5V.