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AMDGPU To Allow Memory Re-Clocking Soon For Multi-Monitor Setups

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  • AMDGPU To Allow Memory Re-Clocking Soon For Multi-Monitor Setups

    Phoronix: AMDGPU To Allow Memory Re-Clocking Soon For Multi-Monitor Setups

    Currently the AMDGPU Linux kernel driver doesn't automatically adjust the video memory clock speeds when running a multi-monitor setup since it's more complicated to gracefully handle when scanning out to two or more displays. But a set of currently experimental patches will allow memory clock switching support on multi-monitor setups with the AMDGPU DC code...

    http://www.phoronix.com/scan.php?pag...tor-vRAM-Clock

  • #2
    Windows user have been complaining a lot about this, they will be envious!

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    • #3
      What I hate is that since Linux 5.0 or so, it seems that the driver prefers clocking the graphics core over the memory, causing the speedometer in my card to go up even when watching a video, wasting energy (it easily reaches 50°C when this happens). This wasn't the behavior in Linux 4.18.

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      • #4
        Right now the video memory clocks are stuck to their highest speeds when in a multi-monitor configuration
        Strange - i'm running two monitors (differing frequency though) and when setting amdgpu.ppfeaturemask=0xffffffff (to have full control over voltages etc), i have strange screen flickering issues that are reported to originate from lower memory clocks - disabling the lower Clock settings (and thus fixating max clock) solves the issue.
        So either using amdgpu.ppfeaturemask=0xffffffff causes a change in multi-monitor memory clock behaviour or there is something other going on.

        Does anyone have information about how the higher memory clocks affect power consumption? i can't imagine it having a huge impact?

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        • #5
          Originally posted by Termy View Post
          Does anyone have information about how the higher memory clocks affect power consumption? i can't imagine it having a huge impact?
          It has, because it also affects the memory controller inside the GPU, which probably also has an impact on other features like power gating.

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          • #6
            Originally posted by Termy View Post
            Strange - i'm running two monitors (differing frequency though) and when setting amdgpu.ppfeaturemask=0xffffffff (to have full control over voltages etc), i have strange screen flickering issues that are reported to originate from lower memory clocks - disabling the lower Clock settings (and thus fixating max clock) solves the issue.
            So either using amdgpu.ppfeaturemask=0xffffffff causes a change in multi-monitor memory clock behaviour or there is something other going on.

            Does anyone have information about how the higher memory clocks affect power consumption? i can't imagine it having a huge impact?
            The flickering occurs because the memory speed is changing at between 73-78 Hz, so 60 and 144 Hz monitors never see it. And to answer your question about the power draw, on an 8gb RX580, the difference is between 15-20 watts depending on the specific AIB
            Last edited by Snaipersky; 08-23-2019, 10:14 AM.

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            • #7
              On my RX 470 4GB having the MCLK stuck at 1650Mhz reports around 23 Watts of power usage in `/sys/kernel/debug/dri/0/amdgpu_pm_info` (may be inaccurate), while having it at 300Mhz lowers VDDGFX by 200mV and drops to around 8 Watts reported power usage. This makes a vast difference in idle noise due to the lower fan speed required.

              AFAICT setting `amdgpu.ppfeaturemask` to `0xffffffff` force-enables PowerPlay and therefore MCLK switching even on unsynced multi-monitor setups which leads to screen flickering. This issue is tracked in this kernel bug.

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              • #8
                Originally posted by Snaipersky View Post
                The flickering occurs because the memory speed is changing at between 73-78 Hz, so 60 and 144 Hz monitors never see it. And to answer your question about the power draw, on an 8gb RX580, the difference is between 15-20 watts depending on the specific AIB
                That's not true, i'm running a 144 and a 60Hz Monitor and get the flickering if i don't disable the two lower memory clock settings.
                15-20W is more than i would have imagined i must say...

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                • #9
                  Would this allow for multi-monitor freesync as well?

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                  • #10
                    The way I've worked around this is to force either the low power setting (desktop) or high power setting (games) using Radeon profile. I have 2 60hz 1080 screens attached to my rx460 4gb.

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