Question what is determining the 8bpc or 10bpc? is it the refresh rate or the driver?

csm101

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Hi All

i have a monitor that can run on 120Hz@4k. in that rate how ever the bpc drops to 8. while in 60hz i can select 10bpc. so i like to know what is determining whether i can set the bit depth to 10 or 8? i tried a custom 4k res where the refresh rate is 90. in that i was able to select 10bpc but it never set when i press apply. my h/w setup in the signature.
 

csm101

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You should post your specifications not in your signature because not everybody reads signatures
you mean the lines after my single line? ok. here's a copy paste.

Asus z390-P, intel i5 9400, corsair vengence RGB DDR4 16GB*2 @ 2666Mhz, EVGA RTX 2070 black edition, ADATA XPG 240GB NVMe SSD,WD 1TB HD,ADATA XPG Pro 1TB NVMe, samsung evo 850 250gb SSD, Corsair graphite 760T white enclosure, Logitech Z5500 sound system, Acer Predator XB3 monitor,Corsair STRAFE RGB MX RED key board, Logitec G502 protius core mouse, corsair RM750x white PSU
 
Hi All

i have a monitor that can run on 120Hz@4k. in that rate how ever the bpc drops to 8. while in 60hz i can select 10bpc. so i like to know what is determining whether i can set the bit depth to 10 or 8? i tried a custom 4k res where the refresh rate is 90. in that i was able to select 10bpc but it never set when i press apply. my h/w setup in the signature.
I'm assuming you are using HDMI?

The root issue is bandwidth; HDMI 2.0 simply can't drive 4k120, 4:4:4 at 10bpc. You can do 10pbc if you drop the chroma down to 4:2:0. Note this assumes no HDR; with HDR the only way to get 10bpc out of HDMI 2.0 is to drop down to 4k60.

https://en.wikipedia.org/wiki/HDMI#Refresh_frequency_limits_for_standard_video

https://en.wikipedia.org/wiki/HDMI#Refresh_frequency_limits_for_HDR10_video

DisplayPort 1.4 has a bit more bandwidth then HDMI 2.0, and can handle 4k120 4:4:4 at 10bpc without issue (I think; I can't find a easy breakout of DisplayPort resolutions @ 10bpc).

The easiest solution is to upgrade to a HDMI 2.1 capable GPU/cables.
 
It's on the DisplayPort Wikipedia page
https://en.wikipedia.org/wiki/DisplayPort#Refresh_frequency_limits_for_standard_video

Color depth of 8 bpc (24 bit/px or 16.7 million colors) is assumed for all formats in these tables. This is the standard color depth used on most computer displays.
Gah, wikipedia put the chart under the HDR header and for some reason that chart is mimimized by default (at least for me).

So yeah, neither DP 1.4 or HDMI 2.0 can handle 4k120 @ 10bpc; thought DP could handle that but apparently not.
 

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