4k@144Hz no longer available after upgrade to Big Sur
I have an iHack with a 5500XT and a Pro Display XDR connected with the Belkin VR cable. Works fine at true 6K with DSC in Catalina, but in Big Sur I get 6K scaled with actual output at 4K and DSC disabled according to AGDC Diagnose. Just updated to 11.2 RC (20D53) and the issue persists, unfortunately.
@tim, Apple stiil didn't fix the bug in 11.2 RC
Ah yep. Thanks for that. I just managed to finally test it on my MacBook Pro as well, and can confirm I got the same results.
Well. HOPEFULLY 11.2 will go live to the public this week, and we can only hope that 11.3 will come around soon enough the corner to fix this.
I did some more tests with my iHack running 11.2 RC3 (20D64), and discovered the following: with the ProDisplay XDR connected using the included Apple TB3 cable to a 5500 XT via pass-through with a Titan Ridge card I can get full 6K output with DSC enabled, but with the PD XDR connected direct to the 5500 XT with the Belkin VR cable, I only get scaled 4K output.
I am on 11.2. It is still not possible to do 144Hz at 4K and you are capped at 95Hz with DSC.
e: Got desperate and emailed Craig Federighi. He responded "Thanks for the report."
I just tested the final shipping version of Big Sur 11.2 and can confirm I still had the same issues as before. I've updated my Apple Bug Report ticket to reflect this.
Oh sweet! Well done on hearing back from Craig Federighi! That's certainly a good indication that they're very much aware of this issue.
Welp. Now that 11.2 is done and dusted, we should hopefully be seeing 11.3 beta 1 at some point very soon.
EDIT: *sigh* Tested on Big Sur 11.3 beta 1 that released this morning. Still no change.
Oh yep! I tried it this weekend. Somewhat good news! I can confirm on my end that 11.3 beta 2 brings it back to where it was in 11.0. Where I can actually set my desired resolutions properly again (In this case, 5K but downscaled to a 4K panel), but DSC still isn't enabled so I can only see about 98FPS instead of my usual 144FPS.
It's certainly an extremely good step in the right direction.