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I tried the other DP to DVI adapter (a regular cable with DP on one side and DVI on the other), and the minimum bit depth shown by the

xrandr --verbose

command was 8 for this DP output. I used an RX6600 card for the test. This means not all adapters are suitable for this purpose.

Meanwhile, a Type-C DP (Intel Xe) -> Belkin USB-C Video Adapter -> DVI allowed switching to 6 bits.

It turns out that the minimum 8-bit limitation for HDMI on my Intel UHD Xe (12th gen CPU) is not a hardware issue; it's a driver limitation in both Linux and Windows. In Windows, I was able to force a switch to 6-bit mode over HDMI by writing a specific value to the video controller pipeline state register. The following bits determine the bit depth (the rightmost bit indicates this mode, besides 8 bits, zero is used there):

- 00000100000000000000000001000000 - 6-bit
- 00000100000000000000000000000000 - 8-bit
- 00000100000000000000000000100000 - 10-bit
- 00000100000000000000000010000000 - 12-bit

For my hardware, the value for 6 bits is 0x4000040, and it works for HDMI connection.

P.S. To enable 6 bits over HDMI, I assigned the variable 'New' the value 0x4000040, which was written to the register at this line: https://github.com/skawamoto0/ditherig/blob/master/ditherig/ditherig.cpp#L630C60-L630C63 (this is from the original ditherig app code). I will post the modified source code later in case anyone else wants to experiment.

Here are photos showing the screen in both 6-bit and 8-bit modes over HDMI. Banding is visible in the 6-bit mode:

https://ibb.co/qsGgD4Q

https://ibb.co/0Mjp5Ry

P.P.S. If it works for me, it will most likely work on other generations of UHD as well, although I can't say exactly which ones, since I only have Intel UHD Xe (12th gen CPU) for testing. I'll try to ask friends to find other UHD models for testing.

    Prefer KDE Neon for my eyes. Am convinced KDE Neon (dark) with Wayland is about as good as it gets with my hardware in terms of eye comfort.

      Crunch bang ++. Lightweght Debian Openbox dsitro. Turning off compositing makes it pretty good

        jordan

        Today, my ASRock Arc A770 arrived. It seems that HDMI on it is routed through DP. Check your A770 LE in Ubuntu Desktop (X11); if it's the same for you, you won't have any issues setting 6 bits with the xrandr utility when connected via HDMI.

        They mention here that LE also doesn't have a 'true' HDMI (https://www.vegascreativesoftware.info/us/forum/intel-arc-general-discussion-of-newest-gpu-competitor--140323/), and most likely, inside the graphics card, it is connected via a converter to DP.

        You can check with the command

        xrandr --verbose

        You should see something like "DP-X connected primary…". If you see something like that, you can set it to 6 bits with the command

        xrandr --output DP-X --set "max bpc" 6

        where X is the number of the DP output.

        My HDMI connection is detected as DP-1, which indicates that the HDMI port in it is not genuine:

        DP-1 connected primary 1920x1080+0+0 (0x4b) normal (normal left inverted right x axis y axis) 531mm x 298mm

        Clones: HDMI-1

        max bpc: 6

        range: (6, 12)

        subconnector: HDMI

        P.S. Regarding dithering, I can't say for certain yet. It seems that after switching to 6 bits, everything is okay, but more time is needed for testing.

          WhisperingWind my ASRock Arc A770 arrived

          are you planning to test A770 in win10 builds…? the graphic card looks promising without dithering, compared to nvidia rtx20 and newer series cards

          WhisperingWind
          Wow thats great!! So with modifying the code we could force 6bit without frc or any dithering then? Is there a way to modify ditherig to have options to easily toggle between the different bits ?

          K-Moss ensete
          which gpu do you use ?

          WhisperingWind
          Yup I forgot that they are using a TCON chip to convert dp to the fake hdmi. I think they also state that if you enable rebar in bios that you can use the motherboard true hdmi 2.1 as a passthrough to the arc dgpus. I would like to know if capping it to 6bpc will dither or not since intel default behavior is to spatial dither under 8bpc. Do you find linux to be more comfortable with these edits than windows and the edits?
          I have that incandescent lit monitor I need to try soon so trying to figure out if I should use win or linux. I am super sensitive so I want to stick to the most promising hardware/os for testing.

            jordan

            So with modifying the code we could force 6bit without … any dithering then?

            In terms of disabling dithering for HD/UHD/Iris, it depends on how complete the Ditherig database is. I remember that with the UHD 730, this application didn't help me.

            Is there a way to modify ditherig to have options to easily toggle between the different bits ?

            Yes, I will try to do that. But for now, reliable data is only available for one version of the driver and Intel UHD Xe (12th Gen CPU). In other models, the bit positions may vary or may not work as needed. I will soon be able to additionally check on UHD 630 and UHD 730. Information on other models will have to be gathered through logs (but I don't think the UHD models in the 700 series differ from each other). Modifying the code itself is not a problem; the main thing is to gather information about the bit positions in all necessary models of Intel graphics cards. 🙂

              Yup I forgot that they are using a TCON chip to convert dp to the fake hdmi. I think they also state that if you enable rebar in bios that you can use the motherboard true hdmi 2.1 as a passthrough to the arc dgpus. I would like to know if capping it to 6bpc will dither or not since intel default behavior is to spatial dither under 8bpc. Do you find linux to be more comfortable with these edits than windows and the edits?

              When it comes to Intel UHD Xe, Windows 11 is more comfortable. Although I constantly feel like something is always moving on the screen (even at 6 bits).

              It's too early to say much about the A770 since I've had it for a short time. However, the image with it feels more stable and calm compared to the UHD Xe.

              I have an old motherboard based on the Z390 chipset, and it most likely doesn't support ReBAR.

                WhisperingWind gotcha. I wonder if ditherig has the appropriate edits for Intel iris. I do own a iris laptop(10th gen Intel) I was doubting that ditherig supports arc.

                WhisperingWind
                Usually new bios updates support rebar but I'm not sure if I would ever update to a latest bios since they can bring strain. Instead this i think would be the better option. To add rebar support
                https://github.com/xCuri0/ReBarUEFI
                I was going to use my Intel arc on my z390 mobo and use that to modify my bios to support it since I manually rolled back my z390 to the very first bios version with a cha341a programmer (super easy)

                Definitely let me know how win11 feels! Seems like disabling ACM does more with the arc. If you plan to try win10 the minimum version supported is 20h2 which supposedly is safe to many. I do wonder if we can modify the Intel driver to install on 1507 or 1511 win10(most safe). Maybe even modify a very old Intel driver adding the arc hardware ids to it to support it on older os. (I'd pay for this lol)

                  jordan

                  I'm not sure if modifying the driver will require reverse engineering the application, which I believe is against Intel's policy. For now, I'll explore less invasive methods on Windows 11 to see if anything works. I couldn't find an option to switch between 6, 8, 10, 12-bit modes in the A770 control panel, so I may need to find an alternative solution.

                  I'll make sure to update you tomorrow or on Saturday with the testing results. I just need a little time for my eyes to adjust.

                    WhisperingWind oh okay I didn't know that. Sounds good! Curious to also hear if either win or Linux feels best

                    jordan currently i use zorin os(based on ubuntu) which uses x11, still feel some levels of discomfort(less when using white text on black background) , but

                    • There are a lot of reflection in the room i use my desktop, so this could be it
                      *
                    • I've read conflicting information whether the display is 8-bit or 6-bit with frc.
                      *

                    ensete is that the bookworm 12.1 version? I forgot about this distro. I remember someone posted about it awhile back as something very lightweight. Maybe that's the way to go as a start for me then. I wonder if gnome could cause issues

                      dev