You can try the following methods to upgrade the BIOS:
As per your description I see it is working fine over DP but have you tried different HDMI cables?
It WAS working over DP, until I disabled DP in the bios in an attempt to get it to work over HDMI (which albeit was dumb, but it shouldn’t be so easy to lock myself out of the bios like it did because the HDMI port won't display the bios – is there any key I can press, like F2 to enter the bios, that resets all the bios settings to defaults when I can’t see the bios display?)
My friend next to me in the lab brought his NUC and hdmi cable in today (he's one of the ones with the problem that the Crucial ram sold in the EPP store (CAS 11) will only work with 1 stick in the bottom slot - I bought slightly different (CAS 9) Crucial memory which works properly) . We're going to do some experiments later this afternoon (as he's also having a lot of trouble getting good video decoding in windows, whereas on mine any H.264 content, even 4K, decodes with very little CPU usage in Linux with XBMC, HEVC not as much, but of course there's no full hardware decode of HEVC in broadwell), but both of us need to get some work done first. I'll try his cable and see if it makes any difference. He said that he can definitely see the BIOS display over HDMI on his unit. Seeing as my cable works correctly at 1080 once Linux boots, I don't really see how it could be a cable problem at any lower res, but you never know!
As for the bios upgrade methods:
Express Update: No Windows
F7 Flash Update: No display (unless I can do it blindly by assuming the first device on the first menu is the USB key, and the file will be chosen on the second menu by default?)
Power Button Menu Update: No display. Just tried it, I can hear the beeps, but can't see anything
iFlash: No display - can't see anything
Recovery Bios Update: This one probably actually has some hope - if it comes to it, I'll give that method a try.
I'll post an update after I try a different HDMI cable, or try the recovery bios flash - hopefully later this afternoon.
My friend next to me in the lab brought his NUC and hdmi cable in today (he's one of the ones with the problem that the Crucial ram sold in the EPP store (CAS 11) will only work with 1 stick in the bottom slot - I bought slightly different (CAS 9) Crucial memory which works properly)
Would you mind sharing the type of Crucial memory? Was it the Crucial Ballistix Sport DDR3 1600 (PC3-12800) CL9 204-pin SODIMM Memory BLS2K8G3N169ES4 ?
So, it really was the HDMI cable. Strange that it worked at 1080, but not at any other resolution, yet the other cable (exact same one from Amazon) did! Learned something new today! Must've been one of the i2c pins that wasn't connecting or something. Thanks Amazon! Should've stuck with my usual budget cable supplier, Monoprice. Changed the bios back to DP, so I can actually see it with a DP->DVI adapter for now until I get a new cable.
My apologies for being rather harsh initially to the NUC team!
Nixiedesk: yeah, not really sure why I needed 8GB of ram for XBMC/KODI, but if I ever need to use the NUC for something else, it'll have plenty! Just running Debian (well actually the Cinnamon version of Siduction, so lightweight DE) and Kodi, it uses about 700MB of RAM. Pretty sure OpenElec would be even less, but full Debian is so much more flexible. I was wondering why you'd need 16GB!!