Question Updated to RX5700XT and new LG LG 34BL850 ultrawide. 6bit color vs 10 bit color

[CuriousMike]

Recently did a small upgrade for the home office / game machine and updated two pieces at once.

I have the monitor connected to the card over DisplayPort.

I was able to use the AMD software to create a custom profile that runs the display at 75hz.

However, when running at 75hz, the color depth drops to 6bpc and refuses to move to 8 or 10.

If I run at the default 60hz, I can select 10 bpc.

Is this a limitation of DP bandwidth, or other?

 

[Stuka87]

If you had a standard 2,560 x 1,440 display, you could do 75Hz with 10bit color (thats the max for DP1.2). But it looks like you have an ultrawide, going off your screenshot. You can try messing with the subsampling, maybe use 4:2:2 or 4:2:0. This will use less bandwidth.

 

[CuriousMike]

The monitor shows DisplayPort 1.4, does that change the bandwidth?

 

[Stuka87]

The monitor shows DisplayPort 1.4, does that change the bandwidth?

It does, by quite a bit. DP 1.2 is 17.28 Gbps. DisplayPort 1.4 is 25.92 Gbps. Is your cable 1.4 compatible? I know the 5700 XT has full 1.4 support.

 

[CuriousMike]

I didn't know the cable made a difference. I'm using my original DP cable, I'll try using the supplied cable.

 

[CuriousMike]

Well I used the supplied cable, and no difference.
Damnit.
The cable does seem thicker than my old cable.
I don't get it.

 

[CuriousMike]

So using AMD's software, I've created 72, 70 and 65 hz and they all fail to go beyond 6bpc.

 

[Stuka87]

Looking at the monitor's specs, its only rated for 60Hz operation. Its quite possible the display cannot support more than 6bpc when you go over 60Hz. When you start to overclock a display, anything its rated for kind of goes out the window.

 

[CuriousMike]

Right. I suppose if I was more of a gamer I would have prioritized refresh rate.
I'm happy enough with the display @60hz and full colors.

Thanks for your help.

 

[CuriousMike]

As an FYI, I discovered that there exists an AMD bug where creating your own profile forces the display to 6bpc.

https://www.reddit.com/r/AMDHelp/comments/euye38

 

[Stuka87]

As an FYI, I discovered that there exists an AMD bug where creating your own profile forces the display to 6bpc.

https://www.reddit.com/r/AMDHelp/comments/euye38

Ahh interesting. Would be worth submitting a bug to AMD if they don't have an official known issue posted for it.