I'm not sure that Apple have the knowledge or expertise to fix this. I rolled back to Mojave and don t miss the hype of Catalina or BigSur because I'd rather have a stable and functional mac. assisted me with this a long time ago as he has way more knowledge in this area than myself.

Anyway, Mojave is unfortunately the last version that seems to be well behaved. I have demonstrated to apple that Catalina typically will take HBR2 connected devices and move them to HBR if there is any negotiation required on the connection. With Catalina, it will typically reduce the max line rate to HBR meaning that your into low res mode. I've provide Apple outputs of Mojaves well behaving dealings with connected devices and that of Catalina. If you run AGDCDiagnostics you can see that at times Catalina decides to overwrite the Max Line Rate that a connected device can support, or at least in my configuration. The System report for thunderbolt and the displays are misleading as they are inaccurate and may not represent the actual connection to the device if you are using a Thunderbolt/USB connection to the device. Mojave did not experience the issues that Catalina has. I reverted back to Mojave because of the DisplayPort issues with Catalina. Could be the m/c, the cable or the monitor, I don't know.

I then used monitor's on-screen display to flip-flop between the two HDMI input sources.īonus test: the rMBP Lightning to DisplayPort connection resulted in a broken-up mess, did not work while the HDMI was active on the mini side. I did not reboot the mini or the monitor, just pulled the workaround cable and plugged in two HDMI cables I had laying around. I just mention this in case anyone that is using the workaround, USB-C to DisplayPort- or HDMI, wants to give HDMI to HDMI another shot. It's been solid for all of half an hour will have to see how reliable it is over time. To my mild surprise it is working but only at 30 Hz which I assume is a limitation of the rMBP 2012 since I swapped the two m/c's input ports and still only got 30 Hz So I left the mini plugged-in to HDMI-2 and plugged in my rMBP mid-2012's HDMI port to the monitor's other HDMI port, HDMI-1, to see if I could switch back and forth between the two sources using the monitor's on-screen display.

Resolution: 3840 x 2160 (2160p/4K UHD 1 - Ultra High Definition)įramebuffer Depth: 30-Bit Color (ARGB2101010)

Metal: Supported, feature set macOS GPUFamily2 v1 Monitor is a Samsung U32J59x, cable is plugged into the monitor's HDMI-2 port. I just retried the HDMI to HDMI connection from my mac mini 2018 running 10.15.3.

Samsung syncmaster s22b300 driver