Update (11/16/2016): I just realized that I never posted a fix for this. We ended up having to get a high quality DisplayPort cable that had good grounding to get this issue resolved. We went with a 6ft Cable Matters cable from Amazon. Since then the issue has not presented itself.
Yesterday my little brother Doug (aka TopHattWaffle) called me with a weird issue on the new system that I helped him tweak. We swapped out his older Core i7 3820K and its X79 motherboard with a new Z97 board (Gigabyte Gaming 7 Z97X) and a Core i7 4790K. The system was working perfectly and quick at my place with no issues. He brought it home and once he got all his monitors and other devices connected is when the issues started. Instead of going in depth of each step and different things we tried I am going to just put a bullet point list below.
Here is the issue: When the ASUS PG279Q is connected to the system through the main GTX 970 video card and the system is restarted (particularly on a cold boot) the BIOS hangs and reverts to defaults (peripheral settings, overclocking, preferences, etc).
- This does NOT happen when the monitor is disconnected and others are connected.
- This is reproducible on-demand 100% of the time.
- NZXT H630 Case
- Gigabyte Z97X Gaming 7 Motherboard
- Intel Core i7 4790K
- Dual Gigabyte Gaming G1 GTX 970
- Corsair H115i Cooler
- 32GB DDR3-2400 Corsair RAM (4x 8GB)
- Samsung EVO 850 512GB SSD
- 3x 1TB in RAID 5 (Intel RST)
- SteelSeries Apex Keyboard
- Logitech G700S Mouse
- Asus PG279Q over DisplayPort
- HP ZR2740W over Dual Link DVI
- HP ZR2740W over DisplayPort
Troubleshooting Steps Attempted (None Worked/Changed the Outcome)
- Removed all RAM but 1 stick
- Tried another stick of known good RAM
- Disconnected ALL drives from motherboard
- Swapped Video card slots
- Ran only 1 video card
- Flashed Motherboard BIOS from F8 to F7 version
- Flashed video card BIOS to stock GTX 970 version
- Removed ALL USB devices including keyboard and mouse
- Removed all USB devices excluding keyboard
- Connected ASUS PG279Q to HDMI (no video at all)
- Factory reset motherboard BIOS
- Checked CMOS Battery voltage (it was OK)
- Switched active motherboard BIOS to backup BIOS
- Checked and re-seated all power cables
- Deleted and re-created Intel RAID arrays
- Reinstalled Windows from new installation ISO and media
- Wiped ALL drives in the computer
- Reinstalled Windows and tested issue with NO drivers installed
As you can see we have tried to cover all our bases but no matter what the BIOS will always crash and reset when the ASUS PG279Q monitor is attached to the system. We can restart over and over as many times as we want with the other monitors connected with no issues but as soon as the ASUS is connected it starts.
I have never seen an issue like this. I have a feeling it is something to do with the UEFI BIOS crashing for some reason due to the ASUS monitor and causing the reset. Given the lack of logging and the Gigabyte DIAG LED not being of much use we are grasping at straws. We did order a new GTX 1070 to see if the same thing happens, if it does we will be replacing the motherboard next.
Here is a video demonstrating the issue:
Here is the Gigabyte BIOS DIAG LED when it resets to default.
You can see it reset when the DIAG light shuts off and comes back up. The BIOS codes are ambiguous at best.