If I switch my the external monitor to 85 Hz, it goes really weird.

What does it need to support an lg uhd with 85 Hz?

MacBook Pro 2019 i7 16 GB & lg gk950-b

  • Are you using a resolution officially supported by the graphics card in your Mac? – Thorbjørn Ravn Andersen Jun 18 at 11:42
  • so i opened the display setting did scaled and 85hz was in a drop down, now that makes it appear that the internal graphics """"officially"""" support it (if it looks like a duck, it should quack like a duck). But as I found out it doesn't. Took and hour of safe boot nvram and pram resetting and factory reset on the monitor. just by switching to 85hz – Ourjamie Jun 20 at 8:38
  • Look at the specifications. – Thorbjørn Ravn Andersen Jun 20 at 8:46
  • I've added an answer @ThorbjørnRavnAndersen - the easy way is bring an external GPU and if the app doesn't select it - then use macOS to prioritize the eGPU and connect the display to that renderer. Sorry for neglecting to +1 your post till now Ourjamie - it's a very good question, phrased well. – bmike Jun 20 at 12:54

I prefer to drop an external GPU on any Mac where the integrated one doesn’t meet my needs for refresh rate, connected displays or performance. Even a MacBook Air has Thunderbolt 3 speeds to extend performance greatly for storage, arbitrary PCI cards and more. You can upgrade Macs Mini and Air and Pro to add monster-sized 3D rendering cores with robustly connected fast storage through one cable if you choose thunderbolt daisy chain hardware.

Apple sells only a few eGPU direct to consumers and most are out of stock at present, but third party options are widely available and allow you to pick and choose your construction, support and features. Apple even calls out a few dozen models and AMD in particular as recommended models.

Since macOS Mojave 10.14 there is robust software support for preferring the external GPU even if the app you run might not yet check for this option.

Option for macOS apps that don't auto select from multiple detected GPU

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  • My MacBook Only has usb-c. – Thorbjørn Ravn Andersen Jun 20 at 13:10
  • Mine too @ThorbjørnRavnAndersen - I let that one stick at 60 Hz and one 4K display most of the time. At work, we keep the MacBook to one display and no rendering / faster refreshes. – bmike Jun 20 at 13:34

The max refresh rate remains 60Hz.


Available refresh rates You can switch between these refresh rates on your Retina display:

  • 60 Hertz
  • 59.94 Hertz
  • 50 Hertz
  • 48 Hertz
  • 47.95 Hertz


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