Analysis of images from various graphics cards

simplex

Is any difference in old rx 6600 and new one ?

The old graphics card was worse. But I don't remember exactly whether I set it to 60 Hz or 59.94 Hz; and could this have affected the result.

The new one is perfect for my eyes.

Monitor (now 6-bit, before were 8-bit), cables, TV, card vendor, PC hardware….?

Both cards are Sapphire AMD Radeon RX 6600 PULSE.

I updated the BIOS from the 2019 version to the 2023 version. The hardware has not changed (described in the first post), but the cable was replaced with a UGREEN (HDMI 2.1). The old one was an unnamed Chinese cable, but it was also fine; I tested it with the new graphics card.

I use Sony KD-49XG8096 TV (manufactured in 2019) as monitor for my PC; the display is true 8-bit.

Btw, does you ram really run at 3200 XMP at 1.2V? Wow

The BIOS shows 1.2 V, but there might be an error, and it could actually be 1.35 V.

simplex

I currently do not own any RTX 20 series cards, but if I ever acquire one, I will analyze it.

Previously, I had a PNY Quadro T400 in my work PC, and it strained my eyes even in the BIOS.

I compared images taken using an HDMI recorder on Linux Cinnamon 22.1. Test subjects: ARC A770 and UHD 630 (i9-9900K). The settings used are: 8-bit, dithering off, and Broadcast RGB set to Limited.

In the archive, you will find simple comparison reports for three pairs of images. Including the compared images; all images in the report are clickable.

For the first pair of images, 8 differing pixels were found. The differences equal ±1 for each component (R, G, or B).

For the second pair of images, 1901 differences were found: 1900 pixels differ by ±1 for each component (R, G, or B), and one pixel differs by ±2 for each component (R, G, or B). All 1900 differing pixels form a small horizontal line drawn in the settings application.

For the third pair of images, only one differing pixel was found, with differences equal to ±2 for each component (R, G, or B).

Despite the different architectures of the GPUs, they produce nearly identical visuals in Linux Cinnamon 22.1 overall.

karut

How did you disable dithering on Linux on Intel GPUs?

When using an Intel GPU/iGPU in 8-bit mode or higher, dithering is disabled by default on Linux. In 6-bit mode, dithering is enabled, but there is a fix to disable it.

Is there a difference in output between Windows and Linux?

I haven't tested it in detail yet, but it should be. It doesn't necessarily have to lead to eye strain, just slightly different shades due to the different color schemes in the drivers, etc.

Which would you say is more comfortable?

My experience might not be entirely relevant since I use an Apple Silicon Mac 90% of the time, and the PC is connected to a TV for gaming and YouTube.

Previously, I used a mini PC based on the i5-12450H (UHD 48EUs) with Linux Cinnamon 22.1 and Windows 10 22H2, and it was equally comfortable in both operating systems. However, it recently stopped turning on after a power surge. Now I use an RX6600 and Windows 10 22H2. The second setup seems subjectively a bit more comfortable to me.

Have you tested the same GPU with different distributions or desktop environments?

Haven't tested it yet. It's more difficult, as different compositors and desktop environments will introduce significant inaccuracies in the test. But theoretically, it can be attempted using calibration images opened in full screen. For example, comparing contrast and brightness may not be valid due to the predominance of lighter shades in the interface of one of the desktop environments. In general, this requires some thought on how it can be done.

simplex

Getting a 1:1 image when recording to an HDMI recorder can be a non-trivial task, as the driver-GPU combination might apply its own color correction. For instance, on Linux, Intel UHD 48EUs and Intel ARC A770 render almost identically. However, in Windows 10 22H2, even when both GPUs use the same Intel UHD driver, the difference between the two GPUs is much more significant. The driver might recognize the GPU model and load a custom LUT for color correction.

Dithering, for example, is supposed to have a specific structure, such as random noise to smooth gradient transitions or a checkerboard pattern to improve color reproduction. I think that individual altered pixels cannot be attributed to either of these. This suggests that it is either a calculation error or additional color correction.

Unfortunately, I no longer have the screenshots taken from the Intel UHD 48EUs, but I do have a screenshot taken from the Intel UHD 630. Previously, I compared the Intel UHD 630 and Intel ARC A770 on Linux, and they rendered almost identically. Here's a comparison on Windows 11 (UHD 630 vs. ARC A770): the difference is noticeable to the naked eye (different drivers, different final color processing). In other words, the driver itself can make adjustments to how the GPU renders.

P.S. I’ve encountered strange rendering behavior when comparing screenshots from Intel UHD 48EUs and ARC A770 on Linux, captured using an HDMI recorder. This is not exactly the same issue you mentioned, but it might be related. The screenshots are nearly identical except for the bottom panel (including different icons and time) and the mouse cursor. In the top-left corner, there are small lines of red dots - these represent differences in pixel colors between the two screenshots. These differences are consistent; you can minimize the browser, close it, open any other program, and these lines will remain in their original state. After a system reboot, they may disappear or reappear. This is also not dithering and seems to be some kind of rendering glitch (software or hardware).