eGPU and Display Port

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eGPU and Display Port

I have the i7 2018 Mac Mini (32 gb RAM) running Catalina. I also have the Razor Core X with an MSI Radeon 5700. Both the Mini's and the Radeon's HDMI are connected to my LG 4k 27" monitor. It defaults to the Mini's internal graphics, but both GPUs are active and show up. I found if I didn't plug the Radeon into the monitor, the Mini didn't seem to see it.

I thought the Radeon would be a graphics powerhouse, but so far I'm underwhelmed. Even when I check off "Use external GPU" on some apps, they exhibit really low frame rate. So I decided to try connecting the Radeon through its Display Port, into the Display Port connection on my LG. So I first disconnected the Radeon in the dock, unplugged its HDMI and then connected the Display Port cable. When I did, the Mini went berserk. It began rapidly flickering, the screen turned off a few times and then the Mini completely crashed and shut off. That was a bit unexpected. So I thought that maybe I couldn't have HDMI and Display Port connected at the same time. So I unplugged the HDMI from the Mini and rebooted. The login screen appeared, but with no icons, just the wallpaper backdrop. I used my cursor keys and was able to log in blind. The computer booted to my desktop, but with no files there and no menu bar.

So here's my question: Is Display Port a bad idea for eGPUs? I was hoping it might give me a better frame rate than HDMI.

Posted on Dec 19, 2019 11:44 AM

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Answer 1

Best reply

padams35

Level 4

3,307 points

Dec 20, 2019 7:04 AM in response to Jay Ducharme

I'm using an LG 4K 24" monitor via display port with my 2018 mini (connected to a Sonnet Breakaway Box with a Red Dragon 570). It works fine (but I wouldn't expect any frame rate difference between a GPU's HDMI vs a GPU's DisplayPort).

Defaulting to the internal GPU is normal if the Mini's HDMI is connected to the primary display, and a few brief flickers is normal when the display arrangement changes. I would suggest not connecting one monitor to two different display outputs driven by the same computer.

If you have poor performance and don't see any desktop icons then the mini might think something is connected to it's HDMI port and that that phantom display is the primary (where your login screen, desktop icons, etc are displayed).

If you go to ->System Preferences ->Displays->Arrangement how many displays are shown, and is your LG the primary display? https://support.apple.com/en-us/HT202351

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Answer 2

Jay Ducharme Author

Level 2

195 points

Dec 20, 2019 11:44 AM in response to padams35

I have the Mini and the Core X both connected to my same LG monitor (with the Mini in HDMI1 and the Core X in HDMI2). I can switch back and forth, and there's absolutely no difference in image quality or frame rate. If I unplug the Mini, I don't get a boot screen when I power up. If I unplug the Core X, that graphics card seems to vanish from my list of devices. If I go to my Display Preferences, all I see is the LG with the option to change the text size. There's no scaling option (which I've heard is normal). It's the same on both the Mini and the Core X.

I did discover that the HDMI cable I was using from the Mini was certified only for 1080, not 4k. So I bought two brand new Monster HDMI cables certified for 4k at 60hz. They haven't seemed to make a difference.

The games on Steam (the PC version run through Fusion) still suffer from poor frame rate (about 15 fps), and the only thing I can imagine is that those games (or more likely, Fusion's emulated graphics drivers) aren't able to take advantage of the eGPU. Outside of that, everything else seems to be running okay now.

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eGPU and Display Port

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