Monday, March 17, 2014

Intel NUC - Can't re-enter BIOS through F2

This blog entry is about how I solved the problem where I was no longer able to enter the BIOS using F2 on my Intel NUC D54250WYK.

The problem started when I upgraded my BIOS from 22 to 25 and enabled SecureBoot. Once I did that, the NUC would boot directly into Windows without showing the NUC boot logo nor the F2/F7 prompt.

This is not an uncommon problem. In my case, it took a combination of solutions to solve the problem.

First, the fact that the NUC logo wasn't showing was a clue that the NUC BIOS wasn't detecting the monitor properly. Apparently there's some sort of detection for the monitor to support 1024x768. This detection seems flaky. I tried the DisplayPort connector on two separate monitors without success.

The solution for this problem was to use an Apple mini-DisplayPort to DVI adapter to go from mini-DisplayPort on the NUC to DVI on the monitor. Once I connected the monitor in this manner, the boot screen showed up immediately. I got the idea from this article, which recommended mini-DisplayPort to HDMI.

The 1024x768 detection is particularly problematic if you are connecting the NUC to a TV or through a receiver. In these cases, you may need to connect to a "real" computer monitor.

The next problem was the SecureBoot prevented the BIOS from showing. To solve this it was necessary to enter Maintenance Mode, as described at

Intel NUC - Three flashes and won't boot

This blog entry is about how I solved the problem where my Intel NUC D54250WYK wouldn't boot after I upgraded my BIOS from 22 to 25. (I should have paid to attention to the note that said, "Don't install this if you don't need it." However, I was installing Windows 8.1 and I wanted to make sure I had the latest fixes.)

The symptom was that the NUC would turn on, would flash three times, wait a few seconds, flash three times, and then turn off.

I was running the NUC with 16GB of DDR3 1866 (PC3 14900) Laptop Memory. This memory is faster than most users run, but recent versions of the BIOS are documented as supporting this speed of RAM.

I tried taking out one of the DIMMs, which had worked for me in the past. However, this didn't work this time. (If you try this, make sure you take out the correct DIMM. The NUC will operate on one DIMM, but this configuration is only supported for one of the two slots.)

Eventually I just left the NUC alone for half an hour in its reboot cycle. It eventually booted successfully and the problem did not come back.

Followup, Oct 2014: My system would crash every couple of weeks after I wrote this article. I finally ran Windows memory tests, which failed. I changed the NUC BIOS to slow down the memory and it worked fine after that.