Jetway NU93B-2930 with spurious reboots

[theonetruestickman]

Hey folks,

I picked up a Jetway fanless box for cheap recently, but it won't stay running more than 10-15 minutes. As far as I can tell it's an older rev. of the JBC311U93 box - I don't have the external antenna jacks. Motherboard is NU93B-2930:
https://www.jetwaycomputer.com/JBC311U93.html
https://www.jetwayusa.com/dl/manual/G03-NU93-F.pdf

First thought was overheating but CPU temp wasn't really getting above 40C. There was a ~0.7mm gap between the CPU die and heatsink, so now after shimming it the CPU stays around 25C on all cores and still has the reboot issue.

I've swapped RAM out, removed the onboard MSATA drive, and removed the wifi card. This happens no matter if the machine is booted into an OS or is just sitting in BIOS - still reboots every few minutes, so I'm thinking this points to a hardware issue.

I've also tried multiple power supplies. The board has a 9-24v listed input range, and the same behavior on a 12V AT supply I have on my workbench as a 16.5V IBM laptop adapter. Both should have adequate current capacity for the board (>3A) as far as I can tell and should have fairly clean power. (Caveat - haven't put my scope on the power lines yet. And don't have a digital scope that can trigger/capture.)

I'm a bit at a loss as to where to start, beyond watching power rails. Anyone else seen similar issues or have experience with these boards? Don't see much for Jetway in the search. I was really hoping this thing would work as a compact workbench rig.

[amyk]

Is the interval between reboots nearly constant?

Look for "watchdog timer" or similar setting in the BIOS.

There's a "watchdog sample code" item at the very bottom of that page.

As an aside, I like the instructions for flashing BIOS there:

1. Prepare a MS-DOS bootable USB flash drive.
2. Download the zip file.
3. Unzip the file and copy to the USB flash drive.
4. Reboot the PC into MS-DOS mode and run *.bat in command prompt.
5. Wait in suspense until the update finished.

[theonetruestickman]

Dang, watchdog timer was on, thanks for noticing that. I never knew what that setting was for - guess I gotta learn something new 20 years into computing.  I had discounted that before because it didn't seem like the time was consistent enough but that is now clearly demonstrated my own internal reference issue. I'm over an hour uptime now.

"Wait in suspense" should definitely be used more in technical literature. 

[amyk]

It's a common feature, a lot of SBCs with Atoms have a watchdog. Of course if your experience has only been with more mainstream desktop PCs and laptops, this would not be familiar.