For best viewing pleasure I usually set my monitor to 144Hz and native 1080p. At that refresh rate my RX6900XT draws about 35 Watts in idle situations Memory clock stays at 1000Hz. I have to lower the monitors refresh rate to 75Hz, then the card draws only 8 Watts in idle and memory clock goes significantly down to 96MHz. Using 100 or 120 Hz does not help. Situation in windows is different. The same hardware setup works in Windows10 at 1080p@144 with idle power draw of just 8 Watts. So my guess is this is a driver issue and not a hardware issue.
Hardware setup: Mainboard: MSI MPG B550I GAMING EDGE WIFI CPU: Ryzen 5950X GPU: Radeon RX 6900XT Kernel 5.13.10 mesa 21.1.4 X11
Anything happening with this bug? I noticed the same behavior, but like to add it's fine for me at 100Hz (using ~7W) only at 120Hz it fires up (~35W). I have an AMD RX 6900XT with kernel 5.17.1 and Mesa 22.0.0 (on GNOME/Xorg, Arch Linux).
The driver can only change memory clocks during display blanking periods to avoid display glitches. If the blanking period is too short, the driver can't change the memory clock so it keeps it clocked high. You could try adjusting the modelines for the problematic modes to extend the blanking periods and see if that helps.
I have a similar problem If I use a refresh rate above 90(100,120,144 or 165), then the memory frequency goes up to 1000. The video memory is heated to 60-65 degrees, the GPU temperature is normal. As soon as I set the refresh rate to 90 or less, the memory frequency drops to 96. The GPU memory temperature also drops to 45-50 degrees. The problem exists on the EndeavourOS and Fedora 38 distributions. Mainboard: MSI PRO B650-P WIFI CPU: Ryzen 7600X GPU: Radeon RX 6700XT 12Gb Display: Xiaomi Mi Gaming 27 with DisplayPort connection. Kernel 6.2.8 and 6.1.21 mesa 23.0.1 Wayland 1.21.0 KDE 5.27 or GNOME 43 Tested this problem on Windows 11. Windows 11 set memory clock to 100-200 on 165Hz.