Just got myself a new 4K VA panel monitor and unfortunately could not use it on my main UEFI based rig so I had to salvage my P55 I7-860 system and load Ubuntu 18.04 on it. I knew going in that Nouveau was the number one source of headaches so I disabled it with
Initially, I had a GTX 1060 driving the panel and all was fine. The panel woke up from sleep, showed the BIOS screens and immediately entered BIOS based Grub2 with no issues.
However, (slight tangent) I was going to test my GTX 1080 11Gbps with the new monitor on my actual UEFI rig but that did not come to pass, as Canada Post decided to not deliver ON CHRISTMAS EVE, the day my replacement CPU was supposed to arrive according to the parcel tracking. It still hasn’t shown up and Canada Post took a 3 day break while tons of parcels are backlogged due to a strike earlier in the month.
So I slapped my GTX 1080 11Gbps on the P55 i7-860 system because I had no other choice, and with DisplayPort connected, Grub2 would fail to post. The BIOS screen was fine, but as soon as it got to Grub2, it would hang.
Switched the connectors to HDMI and there were all of a sudden no more issues, but I don’t trust HDMI as much as I do DisplayPort.
Looked online and this seemed to be a common problem with no real solution other than to change GPUs… and was VERY common with 4K panels.
One comment on one of those threads wanted to point out a power rail that the monitor sends BACK to the GPU could be causing some problems. So I turned off the monitor on boot and sure enough… IT BOOTED.
This was also a common solution to those that managed to figure it out.
Also, keep in mind I set
nomodeset, so Nouveau is not a factor in this issue.
My question is, is this exclusive to BIOS based systems or does it affect UEFI the same way? (I have to ask this because the Canada Post strike means I have no clue when I’m getting my CPU for testing the UEFI platform) And if it’s indeed the power rail, would a DisplayPort “condom” (a connector that only carries data, not power, to the GPU) be able to help this situation? HDMI I know carries power through the cable but it has not had ill effect unless you’re connecting a output to an output. This is the first I’ve heard of DisplayPort sending voltage back to the GPU FROM the monitor. I tested with my EDID Emulator to see if the monitor was sending back voltage over HDMI and that was not the case.
This is something I think @wendell should investigate cause the fact that this is affecting POST negatively is worrysome.