Phantom Gaming B850I Lightning Dual GPU

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   Hello, I'm Yuns92 and new to this forum. Unfortunately, my English isn't perfect, but I hope everyone can understand me.

I'm having two strange issues with my new HTPC build:
Components:
- Case: Fractal Design Ridge (White, PCIe 4.0, Mini-ITX)
- PSU: Seasonic FOCUS SGX-750 (750W SFX)
- Motherboard: ASRock Phantom Gaming B850I Lightning WiFi
- CPU: AMD Ryzen 7 8700G (boxed)
- RAM: Klevv Fit V 32GB Kit DDR5-6000 (CL28-36-36-76)
- dGPU: Sapphire Pulse Radeon RX 6800 (16GB GDDR6)
- CPU Cooler: Thermalright AXP120-X67 White ARGB

Note: I delidded the CPU, applied liquid metal for better thermals, and insulated the exposed SMD components on the CPU with nail polish to prevent short circuits.

After a fresh Windows 11 install (fully updated), I enabled the EXPO profile in BIOS for RAM overclocking. I have also updated to the latest BIOS version available.

My goal: A dual-GPU setup using "lossless scaling" (dGPU renders games, iGPU handles frame generation).

Problem 1:
When using the motherboard's HDMI output (iGPU), I cannot select 4K@120Hz on my TV. This is unexpected since both the motherboard and 8700G's iGPU support HDMI 2.1. Works flawlessly via the dGPU's HDMI port.

Problem 2 (more critical):
If my TV is connected to the motherboard (iGPU) and I set the dGPU as the default "High-Performance GPU" in Windows, any game launch causes a full system freeze (games, Task Manager, all apps). A hard reset is required.

However:
-> Using the iGPU as default (display connected to motherboard) -> games run fine.
-> Using the dGPU as default (display connected to dGPU) -> games run fine.

Troubleshooting done (no success):
- Updated BIOS to the latest version.
- BIOS reset to defaults.
- Use default speed for RAM.
- Set PCIe Gen to 3.0 in BIOS.
- Increased iGPU VRAM allocation.
- Reinstalled AMD chipset + GPU drivers.

I'm out of ideas. Has anyone encountered this or know a solution?

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Yuns92 Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 5 hours 25 minutes ago Status: Offline Points: 15	Post Options Post Reply Quote Yuns92 Report Post Thanks(0) Quote Reply Topic: Phantom Gaming B850I Lightning Dual GPU Posted: 3 hours 20 minutes ago at 8:42pm
	Hello, I'm Yuns92 and new to this forum. Unfortunately, my English isn't perfect, but I hope everyone can understand me. I'm having two strange issues with my new HTPC build: Components: - Case: Fractal Design Ridge (White, PCIe 4.0, Mini-ITX) - PSU: Seasonic FOCUS SGX-750 (750W SFX) - Motherboard: ASRock Phantom Gaming B850I Lightning WiFi - CPU: AMD Ryzen 7 8700G (boxed) - RAM: Klevv Fit V 32GB Kit DDR5-6000 (CL28-36-36-76) - dGPU: Sapphire Pulse Radeon RX 6800 (16GB GDDR6) - CPU Cooler: Thermalright AXP120-X67 White ARGB Note: I delidded the CPU, applied liquid metal for better thermals, and insulated the exposed SMD components on the CPU with nail polish to prevent short circuits. After a fresh Windows 11 install (fully updated), I enabled the EXPO profile in BIOS for RAM overclocking. I have also updated to the latest BIOS version available. My goal: A dual-GPU setup using "lossless scaling" (dGPU renders games, iGPU handles frame generation). Problem 1: When using the motherboard's HDMI output (iGPU), I cannot select 4K@120Hz on my TV. This is unexpected since both the motherboard and 8700G's iGPU support HDMI 2.1. Works flawlessly via the dGPU's HDMI port. Problem 2 (more critical): If my TV is connected to the motherboard (iGPU) and I set the dGPU as the default "High-Performance GPU" in Windows, any game launch causes a full system freeze (games, Task Manager, all apps). A hard reset is required. However: -> Using the iGPU as default (display connected to motherboard) -> games run fine. -> Using the dGPU as default (display connected to dGPU) -> games run fine. Troubleshooting done (no success): - Updated BIOS to the latest version. - BIOS reset to defaults. - Use default speed for RAM. - Set PCIe Gen to 3.0 in BIOS. - Increased iGPU VRAM allocation. - Reinstalled AMD chipset + GPU drivers. I'm out of ideas. Has anyone encountered this or know a solution?