NUC 847 -- Ubuntu -- Disabling RC6 -- ESC Not Recognized at Boot

I own two (2) of the NUC 847 models. Both were purchased same day from same vendor. Based on serial numbers, I believe that they were manufactured on the same day or within the same week.

On one of them I was able to install XBMCbuntu (a special build of Ubuntu which normally boots straight into XBMC) despite the dreaded "RC6 bug." The RC6 bug causes the system to give only a black screen and a mouse cursor after boot. In this state, it is unresponsive to mouse input; it takes an IP address by DHCP but is unresponsive to ping or attempts to connect by SSH. I was able to overcome this bug by pressing ESC during boot and then following the steps outlined at the end of this post. However, the second NUC does not respond to the ESC command during boot (at least, it doesn't give me a Ubuntu command prompt). Pressing ESC on the second NUC does get me to the blue graphic BIOS screen (where choices are F2 for bios settings; F7 for bios update and F10 for boot menu). However, once on this screen, pressing F2 does not get me into the BIOS settings; F7 does not cause a BIOS update; F10 does not open the boot menu. On NUC no. 1, I have never seen the blue BIOS screen.

Q. -- Assuming that I can ever get into the bios (such as by jumpering the bios pins), is there a way to disable the RC6 function at the bios level? If I could do that, I could get Ubuntu running, I believe.

Q. -- Is there an alternate keyboard combo (other than ESC) to get to a Linux command prompt?

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How I fixed ONE of my NUCs (with the excellent guidance of XBMC user Fersken)

This guide assumes that you have already installed XBMCbuntu onto your NUC (either onto a USB flash drive or internal mSATA drive), but found that after installation it does not seem to boot up for you. You either get a black screen with only a mouse cursor in the middle (assuming you have a mouse installed) or only a black screen (if you have no mouse). This guide explains how to fix your problem.

1. Unplug your NUC, count to 5, plug it back in and turn it on.

2. As soon as you turn it on, start pressing ESC every few seconds. One press of ESC should be enough, but it’s hard to tell exactly when to press ESC to get a command prompt, so just do it several times until you see a command prompt.

3. After you do this, you will be presented with two choices that will resemble these:

Ubuntu, with Linux 3.5.0-22-generic

Ubuntu, with Linux 3.5.0-22-generic (recovery mode)

4. Select the first option from the above choices.

5. Press “E” to edit your bootloader setup.

6. After you do this, you’ll see a screen which resembles these two screenshots (my apologies for the poor quality of the screenshots.

7. Look for a line that begins something like, “linux /boot/vmlinuz-3.5.0-22-generic…” and then move your cursor to the end of that line.

8. At the end of the “linux…../boot/vmlinuz…” line, add a space and then “i915.i915_enable_rc6=0”.

9. Press F10 after you have done the above. This will reboot your NUC. When it reboots, you should see a regular XBMC home screen.

10. Press Ctrl-Alt-F1 in XBMC. This will take you back to a Ubuntu command prompt.

11. Type “sudo nano /etc/default/grub”. This will open the Grub file for editing.

12. Look for a line in this file which reads:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

and change it to read:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.i915_enable_rc6=0".

13. Press Ctrl-X (then confirm “Y” for yes) to save your edits to the Grub file.

14. Type the command, “sudo update-grub” and press enter.

15. Type the command, “sudo shutdown -r now” and press enter. This will shutdown your NUC.

16. After rebooting your NUC again, it should go straight to XBMCbuntu. Now you need to change the video settings.

17. Press Ctrl-Alt-F1 in XBMC to go to a Ubuntu command prompt.

18. Type this command, “sudo apt-get install intel-gpu-tools libva-intel-vaapi-driver” and press enter.

19. Press Ctrl-Alt-F7 to return to XBMC.

20. Reboot your NUC.