Custom Resolution Utility (CRU)

[ToastyX]

(10-05-2023 12:20 PM)Dstendo Wrote:  Hello,

I have the Acer XV273K monitor (4K, 120Hz(-144Hz with Dual DP), Ports: 2 x DisplayPort 1.4 & 2 x HDMI 2.0) (https://www.displayspecifications.com/de/model/407f14c5) and a RTX 3080 (Ports: 3 x DisplayPort 1.4a & 2 x HDMI 2.1).
I have had some issues with Black Screens and Alt-Tabbing for a while.
For example, I would Alt-Tab out of GTA V and the screen would go black for a few seconds as if the resolution or refresh rate were being changed. But nothing was changed and it annoyed me.
Then I stumbled upon this Reddit post (https://www.reddit.com/r/OLED_Gaming/com...lttabbing/) where a guy describes my problem and says it's because of DSC. After that, I got into a 4-hour rabbit hole of CRU, and now I know a lot more about it than I would like to.
My issue now:
In CRU if I add a DisplayID 1.3 extension block and add a Detailed Resolution of 3840x2160 with "CVT-RB standard" selected I can use 120Hz and even more with no problems. To avoid DSC, I need to use a refresh rate under 118.2Hz and use 8 bpc and RGB (as per calculator: https://linustechtips.com/topic/729232-g...mulas=show)

as the monitor only has DP 1.4 and the RTX 3080 only supports DP 1.4a. Altough another site says max. 116.8Hz. (https://tomverbeure.github.io/video_timings_calculator) This also works (although between ~117.8Hz and 119Hz I get some weird jittering of the whole screen, so I just use 116.700Hz).

If I select "CVT-RB2 standard" I should be able to go as high as 120.4Hz,
(calculator: https://linustechtips.com/topic/729232-g...mulas=show)
but I can't.
If I use CVT-RB2, the screen goes crazy with artifacts and green colors and flickering as if he doesn't recognize the signal or something. This only happens with < ~60Hz and sometimes up to ~80Hz, and sometimes I can only go up to 30Hz. It's random?

I already tried two different 1.4 DP cables (PI5010-020 & BN39-01879N) and recalculated the values that would be needed for CVT-RB2 (https://tomverbeure.github.io/video_timings_calculator) but they were always correct.

I never use the Dual DP mode in the OSD of the monitor for 144Hz as it activates some input lag.
In OSD, the DP Format is set to 1.4, HDMI Black Level on Normal, FreeSync on On, HDR on Off, 4K-144Hz Mode on Off, Wide Mode on Aspect, Color Space on Standard.
Do some monitors just not support CVT-RB2? Or do I have some other settings wrong?

CVT-RB2 is a newer standard that some monitors don't support, but it's not necessary. You can start with CVT-RB and then manually reduce the blanking/totals to reduce the pixel clock. Those calculators don't tell you the pixel clock limit, which is the most important point. DisplayPort 4-lane HBR3 is limited to 1080 MHz pixel clock at 8 bpc without DSC. Usually it's the reduced horizontal blanking of CVT-RB2 that monitors can't handle, so you can reduce the vertical blanking instead. 4000x2250 totals will get you exactly 120 Hz at 1080 MHz pixel clock. In fact, "Exact" timing already does this, but if you have issues close to the limit, you can try something lower like 4000x2225, which will also give you exactly 120 Hz but at 1068 MHz.