[Not a hackintosh, but] Apple Thunderbolt Display won't wake up after HP Elitedesk 800 G4 BIOS update

[acidrums4]

Greetings, and please excuse me for my broken english and if this is not the place (or the website) to ask for help, as my gear is not actually a Hackintosh. But as I found this awesome thread about setting it on one of the same workstations I got, it's evident you people have a vast knowledge on this. And is not that it seems I will have any luck asking on the HP support forum anyway.

After looking everywhere about what (if any) SFF Workstation could make this Apple Thunderbolt Display work, learned about the HP Elitedesk 800 G4/G5. Could get a G4 SFF, an Apple Thunderbolt 3 to 2 adapter and a HP 4CX35AA PCIe card (from B&H), which after a long shipping wait and some little bumps and hiccups, let me use it in all of its glory with Linux - not everything perfect actually: when power settings turned off the screen, at random times it refused to turn on again. Could not debug or troubleshoot that issue but still everything else was going great.

Now, it was only until past sunday (Jan 16th) I figured out I could update the BIOS from itself, network connection provided. It had 2.14.1 and updated to 2.17.

After that, the display refused to wake up. No HP bootup logo. Nothing.

• Did a BIOS reset - nothing.
• Went back to BIOS 2.14.1 - nothing.
• Disabled power options on the BIOS - nothing.
• Set up the BIOS according to the guide you people offer on your Catalina setup on the little brother of this machine, to the letter - nothing.

It's worth noting that after ending the day's job I switch off the computer and the surge protector. Not into letting the surge protector turned on at night, its noise won't let me sleep comfortably - and always have done that and this was not happening before anyway. The next day when I got to work and turn on stuff is when this happens.

• If I turn off the computer but left the surge protector turned on, the display will wake up normally (or sometimes it will skip the BIOS bootup screen).
• If I turn off both the computer and the surge protector, and switch it on after a short time and turn on the computer again, the display will wake up.
• If I turn off both the computer and the surge protector, and do a 'discharge' of the computer (pressing the power button for 20 secs) and turn the computer on again, the display won't wake up.

From all of the fiddling I have done trying to make it work, discovered that I can only make it wake up after connecting the PC to the TV via a DP-HDMI adapter, and the PC will use the TV as its main display; the bootup process happens, I go to the BIOS setup, exit from there after doing nothing and finally the Apple Display will start working when the bootup process reaches the desktop. If I just plug the TV and let the PC booting up sometimes the screen will wake up and sometimes it won't.

Looked into several places for advice about troobleshooting the Thunderbolt Display, and they talk about resetting the NVRAM and SMC. But it can't find something related to NVRAM for this HP workstation or Linux (and for all of this it seems a BIOS issue, not an OS one) and almost sure SMC is also something related to the OS level.

Again, I'm so sorry if this is not the correct place to ask for this. But it will be much appreciated if you wise people from this forum can give me some guidance about fixing this.

 

[theroadw]

Do you have the option to change the Thunderbolt settings in Bios?
Namely Thunderbolt security should be none and/or legacy mode.
Also Thunderbolt power mode could be a factor if there are options.
It's very possible that Windows or Linux drivers initialize the TB controller and it remains in this state as long as you don't power it off completely.
So it works on reboots or cold boots as long as power wasn't interrupted completely.