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Thread: How Well Is AMD CnQ Working For You On Linux?

  1. #11
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    I just upgraded my kernel from 3.6 to 3.7-rc3 and wondered why CnQ stopped working at all, so I looked into the boot messages and found:
    powernow-k8: this CPU is not supported anymore, using acpi-cpufreq instead.
    As I didn't had acpi-cpufreq compiled into the kernel the issue was found.

    Not sure if I would call that a bad thing through. CPU is:
    model name : AMD Athlon(tm) II X3 455 Processor

  2. #12
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    Quote Originally Posted by pingufunkybeat View Post
    I really do suspect that AMD will find a way to get proper powersaving out for their GPUs.
    But currently they broke already existing code even further . In recent kernels (3.5-3.7 kernels or so), dynpm mode is completely broken for my GPU and /sys/kernel/debug/dri/0/radeon_pm_info could output numbers not matching actual state of things in some cases. Now driver unwilling to reclock GPU to 157 MHz (lowest clock, ok for idle desktop) and only uses 600MHz after boot (far hotter and power hungry mode). Earlier kernels were better in this regard.

    Amazing. I fail to understand: hey, dear AMD guys, why can't you just get some 2-3 GPUs of each 5xxx, 6xxx, 7xxx family and APUs and actually boot some Linux on that hardware to see how it performs? AMD should surely have enough resources for very little test lab where it's possible to see all major quirks in code. But it looks like if it's not a case.
    Last edited by 0xBADCODE; 10-29-2012 at 12:59 AM.

  3. #13
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    Quote Originally Posted by 0xBADCODE View Post
    But currently they broke already existing code even further . In recent kernels (3.5-3.7 kernels or so), dynpm mode is completely broken for my GPU and /sys/kernel/debug/dri/0/radeon_pm_info could output numbers not matching actual state of things in some cases. Now driver unwilling to reclock GPU to 157 MHz (lowest clock, ok for idle desktop) and only uses 600MHz after boot (far hotter and power hungry mode). Earlier kernels were better in this regard.

    Amazing. I fail to understand: hey, dear AMD guys, why can't you just get some 2-3 GPUs of each 5xxx, 6xxx, 7xxx family and APUs and actually boot some Linux on that hardware to see how it performs? AMD should surely have enough resources for very little test lab where it's possible to see all major quirks in code. But it looks like if it's not a case.
    It looks like 4xxx are no better, after setting the profile to mid on HD 4850, I'm still at 625MHz core and 993MHz memory i.e. "the defaults".

    Good thing It's a desktop card and I have dual-slot cooling...

  4. #14
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    This "article" started out ok, but as soon as I got to the first TEST, the lack of intelligence behind it became instantaneously obvious.

    When you put the CPU under LOAD, it ramps up to MAXIMUM POWER CONSUMPTION. CnQ has ZERO effect when the CPU is loaded. You need to test power consumption when IDLE and under varying (controlled) levels of load LESS than fully loaded, and compare the power consumption at the same work loads.

    From personal observation, when unloaded, my AMD CPUs all sit cooly at their minimum frequencies. As others have noted (and mine being no exception), power consumption is drastically better than manufacturer's specs.

  5. #15
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    My personal experience with CnQ is that its doing its job excellent if you do normal work.

    However, if you have full 100% load over large period of time, its better to turn it off and set governor to performance to bump the frequency. This yields in ~10% performance gain over large time period, possibly due to less logic and less ons/offs.

  6. #16
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    Quote Originally Posted by TAXI View Post
    I just upgraded my kernel from 3.6 to 3.7-rc3 and wondered why CnQ stopped working at all, so I looked into the boot messages and found:
    powernow-k8: this CPU is not supported anymore, using acpi-cpufreq instead.
    As I didn't had acpi-cpufreq compiled into the kernel the issue was found.

    Not sure if I would call that a bad thing through. CPU is:
    model name : AMD Athlon(tm) II X3 455 Processor
    Thanks for update.

    "These chips are now supported by acpi-cpufreq, so we can delete all the
    code handling them."

    See here Seems just like code cleaning and move to me.

    Also, here
    " + Support for K10 and newer processors is now in acpi-cpufreq."

    Looks like power management is similar on all Intel, VIA and AMD cpus and they decided to consolidate it into one driver.
    Last edited by crazycheese; 10-29-2012 at 10:22 AM.

  7. #17
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    Quote Originally Posted by droidhacker View Post
    This "article" started out ok, but as soon as I got to the first TEST, the lack of intelligence behind it became instantaneously obvious.

    When you put the CPU under LOAD, it ramps up to MAXIMUM POWER CONSUMPTION. CnQ has ZERO effect when the CPU is loaded. You need to test power consumption when IDLE and under varying (controlled) levels of load LESS than fully loaded, and compare the power consumption at the same work loads.

    From personal observation, when unloaded, my AMD CPUs all sit cooly at their minimum frequencies. As others have noted (and mine being no exception), power consumption is drastically better than manufacturer's specs.
    I thought the exact same thing, but, even while putting the CPUs under load, they still showed some power efficiency which he did point out.

  8. #18
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    Quote Originally Posted by brent View Post
    It's really not, at least not entirely. What the BIOS needs to do for PowerNow/CnQ to work is fill the p-state table in the CPU's model-specific registers, and that's it. This table contain values for operating frequency, voltage, etc. for all states. The OS requires a driver that reads the table and instructs the CPU to switch to a certain state, depending on load, according to some governor. (BTW, if the BIOS fails to set up the p-state table correctly, you can do that from userspace before loading PowerNow drivers.) The transition between states is handled by the CPU itself, so the driver is quite simple.

    Earlier on K8, the driver also needed to accurately do and time all the nitty-gritty low-level details of transitioning between states, and this was quite error-prone, depending on hardware.
    Hi brent I stumbled upon your post while searching the web for a way to fix a problem with my Laptop. I've got a MEDION E1312 with an AMD Sempron 210U and I'm using PeppermintOS 4 based on Ubuntu Kernel 3.8.0.29-generic.
    There are no BIOS Updates availlable from OEM and with my computer your mentioned situation fits my Problem: "BIOS fails to set up the p-state table correctly".
    So how do I setup p-states via userspace? Thanx in advance.

  9. #19
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    Quote Originally Posted by phoronix View Post
    Phoronix: How Well Is AMD CnQ Working For You On Linux?

    One of the latest possible Linux power-related regressions I've heard about is that AMD Cool 'n' Quiet may no longer be functioning too well on Linux-based systems...

    http://www.phoronix.com/vr.php?view=MTIxNjE
    Where are the temps and fan speeds? That's kinda the whole point of CnQ, hence the "Cool"n"Quite"....

    I'm not trying to be mean, but this one was a pretty stupid omission.

    EDIT: I just realized I zombified this thread.... oops, Sorry
    Last edited by duby229; 08-29-2013 at 08:10 PM.

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