MP 1,1-5,1 RX580 4K over HDMI only 30 Hz. Is 60 Hz possible?

[walraven]

My Mac Pro 5,1 has a Sapphire Pulse RX580 8GB which feeds 3 displays:

1. 1680x1050 20" Cinema Display at 60 Hz over DVI
2. QHD 27" LED Cinema Display at 60 Hz over DisplayPort
3. LG 27UD58-B 4K30 over HDMI

I can't seem to pinpoint why the HDMI only allows 4K30 or 1080p60. I have verified that DisplayPort allows for 4K60 from this card, and that I can get 4K60 over DisplayPort on the LG, but my use case requires that I use HDMI to this monitor from this Mac Pro (another device is using the DisplayPort on the LG, the two HDMI are free to use.

I have tried a handful of cables, but I'm not sure if any of them are HDMI 2.0 cables. Could that be the issue? Is there a certain software I should use to force 4K60?

I'm running Monterey 12.6.7 with Martin Lo's OpenCore 0.9.3 package.

Thanks in advance!

 

[chrfr]

3. LG 27UD58-B 4K30 over HDMI

You likely need to enable 4k60 over HDMI on the display itself. For these LGs you need to turn on the HDMI Ultra HD Deep Color setting in the display settings.

 

[walraven]

You likely need to enable 4k60 over HDMI on the display itself. For these LGs you need to turn on the HDMI Ultra HD Deep Color setting in the display settings.

This was it, and my cables are fine. Thank you!

 

[Rico]

You likely need to enable 4k60 over HDMI on the display itself. For these LGs you need to turn on the HDMI Ultra HD Deep Color setting in the display settings.

Holy cow. You've just solved a six years-old dilemma on my 27UD68P. I had no idea of this setting's existence, and blamed my flashed RX 580 for the 30Hz limitation. Just finished rearranging my (6) displays to better balance the load, thanks to you. My WX 4100 runs pretty hot with just one display; three made for a serious heat/fans issue; now it only carries two displays and it's a vast improvement. Mille Grazia!