The "Undervolting" Guide

Discussion in 'Hardware Components and Aftermarket Upgrades' started by flipfire, Apr 1, 2008.

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  1. unclewebb

    unclewebb ThrottleStop Author

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    I haven't had a chance yet to test this but if you go into the Control Panel -> Power Options and use a profile with Minimum and Maximum processor state set to 100% then that might prevent the jumping VID. RMClock could be fighting with Windows 7 for control of the FID and VID when lightly loaded. I'll be testing this out later today. RMClock works with W7, it just needs some tweaks.

    RMClock does not accurately report VID or FID when you are using IDA mode so you might as well enable that multiplier and get some extra performance.

    Of course you have to worry about that. If it is jumping up and down it means that something is not set up right and has to be fixed.
     
  2. Mike570U

    Mike570U Notebook Consultant

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    Ah, well, on my old Clevo it only happens very rarely. But, if you are trying to keep it cool, wouldn't you not want windows to keep the processor at 100% and thus prevent the SpeedStep?
     
  3. NightElfMohawk

    NightElfMohawk Newbie

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    Hi unclewebb,

    I've been using throttlestop with my P8400. I have VID = 0.8750 @ 7.5 multi (2Ghz) and I'm pretty sure it's helping at full load. I didn't notice any difference in power draw at idle either.

    I'm using the 2.0 beta 17 version, but this will expire soon? I'm willing to pay a few bucks for the full version. Dual IDA mode could also be fun to try out.
     
  4. unclewebb

    unclewebb ThrottleStop Author

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    For RM Clock to work correctly in Windows 7 you need to set the Minimum processor state to 100%. This will prevent Windows from fighting with RMC.

    [​IMG]

    If you don't do this then the VID will be jumping up and down higher than what you have it set at.

    You need to do the same thing when using ThrottleStop. If you want RMC or TS to be in control of your CPU then this is the way to do it. This won't put your CPU at 100%. It will just let other programs control your CPU without fighting against the OS.

    Adjusting VID lower definitely makes a difference at full load in power consumption and the CPU core temperature.

    I think I found out the reason why this happens in the newer 45nm CPUs. Regardless of any setting you make in RMC or TS, the CPU will be spending 99% of its time in C3 or a deeper sleep state so all these VID/FID adjustments at idle don't do anything. There might be some tiny power savings but only during the 1% of the time when the CPU is paying attention to your settings. 99% of the time it is doing its own thing and lowering power consumption regardless of how you have it set up. I'll post some more pics of the testing I did a little later.

    NightElfMohawk: If you find a version of ThrottleStop you like and it works OK for you then hang on to it. The recent versions don't expire anymore. I will probably be adding a Donate menu item back in when 2.00 is finalized in the near future. If you want to buy me a beer, I won't complain. :)

    Edit: Here's the interesting test I did. I set the CPU at the maximum FID and VID and set the Minimum processor state at 100% and turned off all the C-State options to force the CPU to run at its maximum. I opened up Performance Monitor and discovered that the CPU has a mind of its own.

    [​IMG]

    No matter what program I used to adjust the CPU, it was still spending 97% of its time in C3 or a deeper sleep state. Performance Monitor is not capable of measuring the time in C4/C6 in Windows so that time gets added to the C3 calculation. When I turned off CPU-Z and Task Manager, it went up to 99%. This has got to be the reason why adjusting VID, etc. gives you zero power savings at idle. The CPU is not using any of those settings the majority of the time because it is in a deeper sleep state.

    This does not apply to the original 65nm CPUs like the T7000 series. You could drop power consumption and core temperatures at idle by adjusting the VID lower but I don't believe this does you any good on the newer 45nm CPUs. More testing still needs to be done to prove this but I found it interesting.

    I think the battery power draw stats in the Performance Monitor might be able to prove what's going on. Time for some more testing.
     
  5. Mike570U

    Mike570U Notebook Consultant

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    Oh, I see. Thanks for the explanation on that. And yes, the T7400 GREATLY benefits from being undervolted. I can surf the web indefinitely while staying below 38*C (100*F)
     
  6. magdelaine

    magdelaine Newbie

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    w00t! Unclewebb, that did the trick. Nice and stable now. Thank you!
     
  7. Ferretwulf

    Ferretwulf Notebook Consultant

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    OMG, thank you!

    Made the change on both laptops last night and no more random voltage changes! Still seems counter intuative, but WTH, it works! Thanks!
     
  8. magdelaine

    magdelaine Newbie

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    By the way, even with undervolting the computer is still too hot for me to work on really. But I find for most of what I do, I can keep it at a "power management " profile set to the lowest multiplier only and not burn my fingers off or set my lap on fire.

    It's a Dell 1640 XPS. Sigh.

    Under power management the core runs at a cool 35c. Without it; it runs about 10c higher just doing normal web/text stuff.
     
  9. ellalan

    ellalan Notebook Deity

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    I have undervolted from 1.1375v to 1.0375 and let RMC to adjust the intermediary voltages, I'm very pleased with the result as it not only reduced my maximum Temp by 12 deg c but also quieten the fan noise.
    Thanks for the great guide.
     

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  10. litaud

    litaud Newbie

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    Great guide! Thanks!
     
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