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Huh interesting. Are these displays all the exact same model?
There’s a relatively new feature in the amd gfx display abstraction layer called freesync power optimisation. This feature leverages panel VRR to help mclk idle low at the desktop. This was introduced for single display use with RDNA 2, and expanded to dual display along with RDNA3s MALL advancements. I’m not sure if this is expanded further with RDNA 4 but I can try to find out.
This isn’t true for Vega 10 and 20 due to their use of HBM2. In general what you’re describing is a comparative weakness of GDDR as a technology. I don’t think there’s anything to suggest there’s an inherent issue with idle power on older gen asics at >60 Hz save from the typical limitations with VBI compatibility in an array of panels or display bandwidth thresholds. In the case of VBI compact issues, modifying EDIDs can indeed help.
That’s kind of curious. I don’t think 3D_FULLSCREEN should inherently determine idle mclk behaviour in and of itself. Is this just a single 1440p display at 120Hz? Is VRR enabled?
huh, I generally expect Vega10 based GPUs to idle at ~3W TGP (not inclusive of other board power losses like VRM). Can you tell us what you display setup is? Can you get a reading of your idle mclk using something like CoreCtrl?
video playback will likely kick the asic out of idle. What’s your power use at true desktop idle?
Generally speaking, vega 10 (56, 64) and 20 (radeon vii) are able to achieve decently low desktop idle with varied display configs due to the memory technology they employ.
Can you tell us which distro and display config this is with?
I’m also in 3D_FULLSCREEN on NV21XT but my idle mclk is 96 MHz. TGP (not to be confused with TBP which is only communicated on RDNA 3 and up) is 6 watts at idle with my browsers open. GNOME 47 + Wayland, 2560 x 1440 @ 180Hz + 1920 x 1080 @ 60Hz, VRR enabled on both displays. This is with Fedora 41, kernel 6.13.6-200.fc41.x86_64
For context, the GPU index (0,1,2 etc) will depend on the number of video adapters you have in the system. If you have a CPU with integrated graphics, there’s a chance this will be registered as 0000 whereas the dGPU will be 0001.
I don’t believe FPO was expanded to >2 displays, though having identical panels would eliminate VBI complexities. Will be interested in understanding how this behaves with rdna 4.