Only 21.6 Gbps for DP 1.4?

[abizo]

Hi guys!

I have this monitor paired with a XFX RX 7900 XT. Monitor has DP 1.4 ports, GPU even 2.1. I have connected it with the cable that came with the monitor, it should be DP 1.4.

The issue is that when I go to the AMD Adrenalin - Settings - Display it shows "Current Link Settings - 5.4 Gbps x 4". That is just 21.6 Gbps and DP 1.4 should be 32.4 Gbps bandwidth. The monitor still runs perfectly fine at 1440p 240hz 10bit with DSC ON. No black screens, crashes or flickering. Is that even possible if the ports/cable are not true DP 1.4?

So I am not really sure if the lower bandwidth values shown by Adrenalin should really be a problem, just wondering what the reason might be.

Thanks!

 

[R-T-B]

DisplayPort 1.4 offers a raw bandwidth of 32.4 Gbps, but the actual data rate is smaller Gbps due to the 8b/10b encoding overhead.

Probably explains it?

EDIT: Still, at >1.2 speeds even you should be getting 8.1gbps per lane... so something is either off or we have an AMD display bug.

 

[abizo]

Thanks for trying to help.

I think I just figured out why the drivers show lower bandwidth.

The reason is DSC. If I turn it off it shows 8.1 Gbps x 4 - that is the DP 1.4 full speed of 32.4 Gbps. So the cable and the DP ports of my monitor are fine, that was my main concern.

Enabling the DSC lowers the requiered bandwidth a lot and that's visible on gpu-z or adrenalin.

But with DSC disabled I can't enable the 10-bit colour depth... I guess 32.4 Gbps are not enough for 1440p 240hz 10bit and DSC should be enabled. Otherwise it is locked to 8-bit.

 

[Event Horizon]

Adrenaline shows 8.1 x 4 for my 4k 144hz with DSC over DP 1.4 monitor. Does your monitor have an option to disable DSC?

 

[abizo]

Yes, I can disable DSC from the OSD menu.

Then it shows 8.1 Gbps x 4 , but I can't enable the 10-bit at 1440p 240hz (stuck at 8-bit). Guess it exceeds the limits of DP 1.4 and DSC should be enabled.

Anyway, if I can see the 8.1 Gbps x 4 with DSC OFF, I guess everything is fine.

 

[Vya Domus]

It shows 8.1 x 4 on mine, 144hz 1440p 10bit full RGB. Maybe the monitor or the mode that's in is not actually 1.4.

 

[abizo]

Mine shows 8.1 x 4 at 1440p 144hz 10bit too. But for 240hz it needs DSC enabled and that lowers the required bandwidth. I guess that explains the values I get.