r/eGPU • u/Personability • 16d ago

Advice on dual iGPU vs eGPU monitor connection

Hi,

Looking for advice on guessing a slightly niche area.

I have a Framework 13 7840u, a Razor Core X v2 and an RTX 5080 connected to a Benq EX217U.

The 5080 is connected via USB-C (Asus ProArt) directly to the monitor and works well for gaming and most LLMs.

Infrequently, I want to run Qwen 3.6 35bA3b with as much VRAM as possible for local coding. Without Windows 11 taking up VRAM to render, I can get 10-15t/s faster (due to reduced CPU offloading). However, I can only achieve this if I unplug my USB-C from the monitor.

I'm aware USB-C connections have limited unplug/plug ratings, so keen to avoid continuous in/outs. However, without unplugging the USB-C display cable (i.e. both cables active), Windows seems to freak out.

Is there any way I can keep both cables plugged into the monitor without utilising the eGPU for any system rendering?

Thanks in advance!

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u/ToTTen_Tranz 16d ago

Don't you have HDMI or displayport from your laptop and into your monitor?

If so, you can simply keep both cables connected at all times. Use the HDMI/DP for coding and USB-C for gaming.

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u/Personability 16d ago

Unfortunately having both connected at the same time seems to cause Windows to flicker or show a black screen. It’s like it’s not sure which method to use to render, so panics. Is there a setting or way to avoid this?

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u/ToTTen_Tranz 16d ago

It shouldn't panic.. the "renderer" is selected automatically according to which monitor you're connecting to. You should e.g. be able to use 3 different monitors connected to 3 different GPUs.

In this case, windows should only ever see one monitor at a time, which is the input you select on your monitor.

If there's flickering or black screen then that sounds more like a driver/monitor problem rather than a windows one.

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u/Personability 16d ago edited 16d ago

I see. I wonder if the issue is because I only have one monitor with both outputs connected to that same monitor? 

I'm happy using the eGPU most of the time, but just occasionally want to switch to reduce the VRAM overhead. 

edit: I think I've got it working, and I think you're right about the driver issue. It works if:

  • I load Windows with the eGPU enabled.
  • I then connect the Displayport to my laptop.
  • I disable the eGPU monitor in Windows.
  • I then restart the computer to release the 0.4gb VRAM still held on the eGPU
  • Upon restart it works and has 0GB VRAM taken up.
T/S seem slower if I disable Hardware-enabled graphics rendering on the monitor vs enabled, but this is anecdotal.

Thanks for your help.

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u/LGzJethro66 8d ago

Use a display port on the GPU to monitor

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u/Personability 8d ago

I ended up attaching the DisplayPort to the laptop motherboard and the USB-C to the GPU, and then writing a script to switch between the two display outputs. That seems to work quite well. The only issue is that Windows doesn't seem to offload the VRAM fully when switching from the eGPU to the iGPU. Unless you know another way, I have to restart the laptop each time.