There is a I2C interface on that chip, for some configuration i think.
It may be another problem than the chip. Till now i found nothing
I took an oszilloscope and did some measurements.
- Original G20CB Bios with Skylake: Visible PCIe data and I2C communication is visible to and from ASM1442 chip. Some initialization parameters. After that, screen comes online.
- Modified G20CI Bios with Skylake/Kabylake: neither PCIe data nor I2C communication.
AND NOW I discovered that G20CI does NOT have HDMI onboard!!! That I could have checked before… I am an idiot!!!
But will it be possible to implement it???
Okay… one issue is eliminated.
Lets head on to the temperature issue, before implementing new features.
Read something, that it is possible that a BIOS is reading the Tj max temperature.
So I booted to Windows, launched Coretemp… indeed. Tj is 100°C. For some reason, Tj max is read as CPU temperature. As a result ASUS Software is reading that Value too.
Coretemp reads out everything correct from the cpu using DTS.
I assume, that something has changed with that SIO chip, that may use the PECI interface (one-wire interface to read-out temps from the cpu). On a G20CI there is a NCT5579 while I have a NCT5568.
So we need to find way to add inHDMI related stuff, not find and edit/carry over settings etc. Good method of testing to figure that out!
I need more time! 
I’ll try to look into all of this soon as I can, but knowing your progress speed lately you may figure it out much quicker than I get into trying to narrow it down
Take the time you need.
Meanwhile I played with the Super-IO issue, replaced the driver and some related PEI and DXE drivers, resulting in non booting bios.
I think I need a dissassembler to disassemble some things…
I wish I could find assembler/disassembler 101 guide!
Did you ever test this Franken BIOS putting back in your other updated vBIOS from G20CB original vBIOS, since it would tie into having HDMI vs the other not, maybe that’s good test to run if you have not already.
Or is current vBIOS updated from your original board already?
The Frankenstein BIOS has the VBIOS from G20CB integrated from the beginning. There is much more missing. Especially the I2C configuration and the PCIe mapping to what ever PCIe port. And, to complete it all, an port entry in the DMI table.
Well that is good to know already original vBIOS. I hope to have time to dig around tomorrow night!
Tried my first disassembling tests… they failed.
They failed in that matter, that uefitool is hanging up itself replacing a patched module.
Currently I am trying to get the SuperIO chip configured correct. I believe, that is the most important thing. I suspect, that the fans are not working correct, too…
You can support the 7 and 8 generation CPU by porting H170I or Z170I BIOS. But some of the functions may have an impact!
I succeeded in lighting this board over 8400!
Which module are you playing with? Did you try just swap it out?
@shixinyuan : thanks, I will have a deeper look on this.
@Lost_N_BIOS : First I tried to swap NCT5779DPeiInit against NCT6792DPeiInit from the G20CB Bios and failed to boot.
Next I swapped everything I saw that has to do something with SIO, there are some PEI and DXE modules, but still failed to boot.
At last I began from the beginning and disassembled booth NCT´s. There are some differences in data but not in the asm-source. So changed the Data and UEFITool gets stuck.
There’s two of those NCT files in your original BIOS, but only one in the frankenbios, did you notice that and test inserting second into missing position?
I see they differ lots though, even for small file, so maybe more than just missing one is issue, but though it might be worth mentioning in case you didn’t notice.
GUID x2 in original BIOS 9029F23E-E1EE-40D1-9382-36DD61A63EAA
I can’t even make a move in assembler, so you got further than I did! I tried hopper and IDA, figured out how to change views a little, but nothing caught in my head for making reasonable edits 
Yes I know that there are two in the CB-BIOS. But CI-BIOS uses only one, why I should insert a second (identical) one, if the BIOS can´t handle it?
Or do I understand something wrong?
I was only thnking your board original wanted used two matching files in it’s BIOS, so thought it would be a good test of two matching files in the fraken BIOS. I’d test two of the original in same location, and then another test with duplicates of the other file in same locations.
Always worth a simple shot first
Ok, I will try it now
Probably wont work that would be too easy, but I always try everything I can think of when it’s safe to play. Sometimes it’s the easy things that beat us up for so long we go crazy!
Okay. In CB bios are 2 NCTs because the next to last volume is a complete copy of the last. But in CI-BIOS the next to last is an empty padding. What i did now, is replacing the NCT in CI-Bios and then copy that region to the empty padding.
But it does not boot.
Btw. the H170I bios mentioned by @shixinyuan is booting, but has issues with the voltage readings. But there are interesting new features inside.
I did notice the volumes are laid out differently in each BIOS, but I thought both were similar as-is both had "two-similar-looking" copies of entire volumes, just in different places.