It is not unreasonable to see temperatures in this range when idle. The temperatures of the other components shows that the thermal solution is being effective. In Small Form Factor (SFF) systems like the NUC, it's a lot tougher to exhaust heat than it is in a large PC with a lot of internal air mass. In the case of the motherboard temperature, the point being monitored is on the opposite side of the board from the processor (and its heatsink/fan unit) and it is passive air that is cooling it. Slightly higher temperatures are thus to be expected.
If you go into the BIOS and sit in the scene that displays temperatures voltages and fan speeds, what are the readings across the temperature sensors that you see? Warning in advance: while in the BIOS, all power management capabilities in the processor are disabled and higher readings than you see in Windows should be expected.
Thanks for the very informative reply. I'll get into the Visual BIOS in the next couple of days after I re-instal Windows 8.1. (I made the mistake of the latest trying Windows !0 preview.) Given the temps of the SSD's and the CPU, I thought things were probably all right, but, as you guessed, I'm not familiar with SFF devices. It's nice to have an informed opinion to bolster my confidence. And, thanks finally for the tidbit about the power management capabilities. I would have hated to see a big, unexplained spike in temps when looked into the BIOS.
FYI - I tested my new NUC5i7RYH at work on an Alioscopic display (one of those lenticular 3D screens that gives you a 3D view without glasses; not as great as one might hope...) running the proprietary Aliomovie software to process a looping demo and it pegged the CPU at 100% and produced temps (using CoreTemp) to just above 100 Celsius. This was using W7-64. The Aliomovie software is CPU intensive and used very little of the 8GB of RAM and was reading data directly off the Samsung EVO SSD.
I also tried the Gigabyte Brix Pro I bought and that CPU did not get pegged, running between 20%-40% and produced temps in the range of about 70-80 Celsius in spite of the much lower CPU load.
Of course the two CPUs are quite different in that the NUC has a dual core and the Brix a quad core. But it's clear CPU intensive tasks are going to heat these things up. I wish the fans were larger and maybe arranged a bit differently to cool better. But for me, using them as HTPCs, this should not be too great an issue.
Just some data points for you...
Thanks for the info. I ordered a set of AC Infinty dual 80mm external fans through Amazon yesterday. . I've been monitoring the temp's on the little thing since I got it. I'm not doing anything CPU intensive, yet, have grown steadily more concerned with its seemingly random temperature spikes. I've been comparing NUC2i7's temp's to those of my Dell M2800 laptop, running an I7 4810MQ. The laptop runs a lot cooler and temps go up and down more predictably. I'll see what the happens when I sit the NUC on top of one of the fans and, possibly, use the other to assist the exhaust.
Sounds as if you have some lovely toys. '-)