Refresh Rate Issue on MacBook Pro M3 Pro with External 100Hz Monitor

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Hi everyone,

 

I’m experiencing an issue with my external monitor’s refresh rate on macOS and could use some advice or insight.

 

My setup:

 

• MacBook Pro 16” (M3 Pro, late 2023)

• macOS 15.3.2

• Monitor: ACER B247Y c3bmiruzxv

• Connection: USB-C to USB-C (using the cable provided with the monitor, which also charges the MacBook)

• Alternative connection tested: HDMI to HDMI

 

 

In macOS display settings, the monitor is set to 100Hz and the OSD on the monitor confirms it’s running at 100Hz. However, there’s no noticeable difference in smoothness between 60Hz and 100Hz. I also tested HDMI-to-HDMI, and the result is the same.

 

When I connect the same monitor to a Windows 11 PC via HDMI, the difference is crystal clear — 100Hz looks and feels way smoother, as expected.

 

So I’m wondering:

 

• Is this a known limitation on macOS with external monitors?

• Could this be a “fake” 100Hz output (e.g. upscaled but not truly refreshed at that rate)?

• Is it a scaling or color profile issue?

• Are there any tools or system settings to verify the actual output refresh rate on macOS?

 

 

Thanks in advance for any help!