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Radeon HD 5770 doesn't downclock when run with 2 monitors

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  • Radeon HD 5770 doesn't downclock when run with 2 monitors

    Hey folks,

    I've been running into a massive problem with power saving with the radeon driver and my HD 5770. I want to report this bug but wanted to check these forums for input first.
    I'm running ArchLinux and the problem is the same with Linux 3.4, 3.5 and 3.6-rc3.
    When plugging in my second monitor (it doesn't even need to display anything and can be turned of in the display settings) my video card fan goes crazy and the card heats up extremely fast.
    I've been using the power saving method mentioned here: https://wiki.archlinux.org/index.php...th_KMS_enabled with profile set to low for a while and it has been working great.
    However when the second monitor is plugged in the card doesn't down clock at all, I've this output from debugfs:
    with both monitors:
    Code:
    [root@jupiter niklas]# cat /sys/kernel/debug/dri/0/radeon_pm_info
    default engine clock: 875000 kHz
    current engine clock: 874960 kHz
    default memory clock: 1250000 kHz
    current memory clock: 1250000 kHz
    voltage: 1200 mV
    PCIE lanes: 16
    directly after unplugging:
    Code:
    [root@jupiter niklas]# cat /sys/kernel/debug/dri/0/radeon_pm_info
    default engine clock: 875000 kHz
    current engine clock: 156990 kHz
    default memory clock: 1250000 kHz
    current memory clock: 300000 kHz
    voltage: 1200 mV
    PCIE lanes: 16
    Is this a known problem or should I report it?

  • #2
    AFAIK, this is normal for the memory clock and the same for me here. The GPU clock should go down with low profile.

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    • #3
      This sounds like normal behavior. Most of the powerplay tables in the VBIOS have a special mode for the single-display case with lower memory clocks, and that is not available with dual displays. It may be that your VBIOS doesn't have a "low power with >1 display" table entry so the choices are limited.

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      • #4
        The memory clock seems ok but it should lower the GPU clock right? I mean with the current configuration my card goes from 55C (it's naturally hot here > 30 C) to over 63 C in less than 10 minutes and makes a hell of a noise.
        So in the end this beefy graphics card is absolutely useless even for desktop use without any gaming... oh hell do I wish there were discrete Intel graphics cards, when a >100 monster occupying 2 slots can't even get me a proper desktop experience..

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        • #5
          Depends on what the card vendor put in the BIOS tables. Sounds like you may have very few entries in the table, ie maybe no "low power with >1 display" entry, which is limiting unless the driver figures out that the higher memory clock and low engine clock make sense to be used together in this case.

          These are the kind of tweaks I had hoped would be happening in the public code over the last couple of years...

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          • #6
            Oh dear, which idiot had the idea to make that stuff card specific and put it in tables of >30 year old technology that's not standardized and totally broken, I need to slap that guy!
            It's a shame how the focus in gaming and performance has produced graphics cards that can't even get non moving pixels on the screen without stupid hassle..
            I wish there was a vendor that just offered a totally dump graphics card but with nice documentation and no legacy stupidty that were capable of supplying a few monitors with pixels..

            By the way, can I upgrade these tables somehow? Like booting with a Windows system and doing some kind of firmware upgrade?

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            • #7
              It has to be card specific -- depends on the cooling solution, power wiring & decoupling, chip bin, degree of mfg testing etc...

              Probably easier to update the driver than hack the VBIOS, and that would benefit more people.

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              • #8
                Is there a way to force the driver to use some GPU frequency, or do I need to get hacking on the radeon Kernel driver? I've been running it on low profile anyway because to be honest what I care about is smooth scrolling in Firefox (which is a catastrophe with fglrx) and smooth desktop compositing (remember Gnome 3 with fglrx).
                By the way it only depends on card specifics when pushing the limits where they don't belong. Look at CPUs they do the same clock speeds no matter what motherboard or chipset. And why the hell can't the chip just measure it's temperature and clock down if it's to high, al Intel TurboBoost and when we are at it, if a graphics card clocks at full throttle when displaying static content, there is no excuse this is just miserable engineering probably caused by wrong goals!
                Last edited by Spacenick; 08-23-2012, 11:56 AM.

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