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Question Black flickering on monitor & total system lockup driving me insane


Mar 1, 2019
Overly thorough explanation:

My PC is 5 years old and may be showing its age, or may not. On Windows 10, I have a problem with my monitor flickering to a black screen for about 2 seconds before recovering, very much like a monitor would during a driver installation. Sometimes, it never recovers and the system completely locks up, requiring a hard restart - the restart button on the computer is often unresponsive and I have to hold the power button to get it to turn off. Sometimes it locks up without a black screen and there is looping audio. The screen flickering is much more common than the lockups, but the lockups are frequent enough that the computer is useless for gaming.

So far, the complete lockups have only happened while gaming. However the black screen flickering occurs even in Windows, almost always when the system is loading something - opening a folder, loading into a new area in a game, etc. However they have also occurred seemingly at random when little was happening on screen.

At one point I ran Memtest86 all night and it completed all 4 rounds of 13 tests and found no errors on any of my 4 RAM sticks. Immediately after rebooting from memtest, new problems began. Big time artifacting occurred in games or videos, any time something was rendered green floating pixels were everywhere but only on the video or game. After switching from HDMI to DisplayPort the artifacting disappeared completely. Soon after, the system completely crashed. Every time I tried to restart the system would bluescreen while trying to POST, giving me INACCESSIBLE_BOOT_DEVICE as an error. I disconnected 3 of my 4 SSDs, wiped the 4th and reinstalled Windows on it. All was well for about 12 hours until I started up 1 game in particular (ES3 Morrowind, an 18 year old game but also heavily modded to look more modern). Within 5 minutes I got the black screen flicker, received another not long after, and reformatted again.

This time I quarantined the drive that contained all my games by disconnecting it, in case it contained a virus. I connected only my 120GB and 250GB drives - both were completely wiped at the time of installing Windows this time. Now I have the black screen flickering big time, had one complete system freeze, and got all of this in the same game that I kept running for 12 hours before with no issues.

My computer has had trouble POSTing for a very long time, at least a year. Upon restart it would fail to load into Windows about 50-75% of the time, always getting stuck at the loading screen for Windows. After reformatting a month ago to try and fix this, the computer failed to post 90-95% of the time. It was a real gamble getting it to boot into Windows, and as a result my computer has been shut off very infrequently over the past year because I'm not sure it's even going to start up again. I ran a dual boot Win 10 / Win 7 setup for 5 years until yesterday. For 3 of those years there were no problems, for about 2 there were POST problems, and each time I reformatted over the past 2 days I installed only Win 10 and have had no POST problems, PC boots into Windows 100% of the time.

I do not know for sure if this is a GPU problem but many of the symptoms look like graphics problems to my untrained eyes. This time I formatted Windows with a highly minimalist setup, two blank drives: one with Windows 10 and downloaded drivers (120GB) and one with a game for testing purposes and Steam with no games installed through it (250GB). My main drive with games, files, downloads, etc (1TB) and my secondary drive with only 1 game on it and some extraneous Directx runtime files (500GB) are both disconnected. The black screen flickering happened almost immediately upon starting up the test game, within maybe 10-20 seconds of getting in game both times I tried, and the first time resulted in a complete system lockup just as before when everything was connected.

I'm at a complete loss as to whether this is a hardware problem or some killer software issue that I just cannot figure out. The black screen flickering continues, for instance it just occurred the second I clicked to Login button on Newegg to look up my computer parts, which are listed below:

OS: Windows 10 Pro 64 bit
CPU: i7-5820K
RAM: 16GB (4 x 4GB) DDR4 2400
PSU: EVGA SuperNOVA 850 G2
120GB Samsung 850 Evo
1TB Samsung 850 Evo
250GB Samsung 860 Evo
500GB Samsung 860 Evo

Sorry for the long post, but I wanted to provide as much detail as possible. I'll be greatly thankful for any suggestions.