Hi everyone!
I'm hoping someone here can help me figure out what's wrong with my PC. I've been experiencing complete system freezes, mainly when running GPU-intensive applications or games, and I'm trying to determine whether my graphics card or power supply is responsible.
I would really appreciate some advice before spending money on replacement parts.
My PC specifications:
- CPU: Intel Core i5-8400
- GPU: Palit GTX 1660 Super
- RAM: 16GB G.Skill DDR4
- PSU: Keep Out FX800B 800W
Current symptoms and gaming performance:
League of Legends:
Runs perfectly without any crashes, freezes, or other problems.
Fortnite – Performance Mode:
I can play for several hours without experiencing any issues. The game runs completely fine.
Fortnite – DirectX 12 Mode:
The entire PC freezes either when I enter a match or when I jump out of the Battle Bus. The system becomes completely unresponsive.
Unreal Editor for Fortnite (UEFN):
Back in March 2026, I could use UEFN without any problems.
Now, whenever I open a template project, my entire PC freezes as soon as the template finishes loading. I can't even start working on a project anymore.
Stress tests I've performed:
1. Windows Memory Diagnostic
- Completed successfully.
- No errors detected.
2. OCCT VRAM Test
- Completed successfully.
- No errors or freezes.
3. OCCT 3D Variable Test
- The entire PC freezes after approximately 1.5–2 minutes.
- The system becomes completely unresponsive.
4. FurMark
- First attempt: The exact moment I started the stress test, my monitor went completely black, the PC powered off for a moment, and then automatically restarted. The test didn't even have time to run.
- Second attempt: The entire PC completely froze immediately when I started the test.
Important detail about the freezes:
Whenever the PC freezes, the screen becomes completely stuck, and neither the mouse nor the keyboard responds. The only way to shut down the computer is by holding down the physical power button for several seconds.
PCIe power connector testing:
I also tried switching to the other 8-pin PCIe power connector from my PSU.
After switching connectors, Fortnite started freezing even in Performance Mode, which normally works perfectly.
When I switched back to the original connector, Fortnite Performance Mode became stable again.
This makes me suspicious of the PSU or its PCIe power cables.
Previous testing and how the problem has changed over time:
More than a year ago, I ran FurMark for approximately 30 minutes without any crashes or freezes.
At that time:
- GPU temperature was approximately 75–85°C.
- CPU temperature was around 75°C.
- The same GTX 1660 Super and Keep Out FX800B PSU were installed.
- Fortnite was already experiencing freezes, even though FurMark worked fine.
In March 2026, I was still able to use Unreal Editor for Fortnite without any problems.
Now, in October 2026, UEFN freezes the entire system when loading a template, OCCT 3D Variable freezes after 1.5–2 minutes, and FurMark causes an immediate restart or complete freeze.
It seems like the problem has gotten worse over time.
What I suspect:
I'm starting to think that my Keep Out FX800B 800W PSU might be failing or having trouble delivering stable power to the GPU.
However, I'm also concerned that my GTX 1660 Super could be developing a hardware problem.
I'm considering replacing the PSU with a new Gigabyte 550W unit, but I don't want to spend money unnecessarily if the graphics card is actually the problem.
My questions:
- Based on these symptoms, would you suspect the PSU or the GPU?
- Could a failing PSU explain why lighter games work perfectly while GPU-intensive applications freeze the entire system?
- Does the fact that changing PCIe power connectors affects stability suggest a PSU or cable problem?
- Does passing the OCCT VRAM test make a faulty GPU less likely?
- Could this be a GPU power delivery or VRM issue rather than a PSU problem?
- What additional troubleshooting steps would you recommend before replacing any hardware?
I'm not very experienced with diagnosing hardware failures, so any advice would be greatly appreciated.
I really want to figure out what's causing these freezes before replacing my GTX 1660 Super.
Thanks in advance for your help!