TDP and Power Limiting (Haswell)

Discussion in 'Hardware Components and Aftermarket Upgrades' started by Dufus, Dec 5, 2014.

  1. Miki.m

    Miki.m Newbie

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    I have some interesting discoveries with i7-6650U in Dell Latitude 7470.

    First was that the ugly CPU performance under GPU is due to really bad Intel Power Balance in accordance with low TDP because GPU eats majority of power causing hard throttling of CPU from up to 3,4GHz to 1,2GHz and under some circumstances even down to 0,5GHz what is really terrible for normal work. ThrottleStop fixes this but unless you run all the time something changes it back to default after some time (I didn’t found it when until now). But this isn’t anything new for audience here I thing.

    More interesting is I discovered that if I Suspend to RAM (sleep) and resume notebook CPU throttling starts to respond to TDP values set up to 20W for PL1 and even 35W PL2. Setting PL1 to more than 20W has no effect and I didn’t test more for PL2 because it has no sense. PL1 values above 15W didn’t persist the bigger the shorter time - 20W just seconds up to 17,5W even minutes then something changed the value usually first below 15W down to even 12W and after few seconds to 15W. It took some time to discover it’s caused by Intel Dynamic Platform & Thermal Framework Driver. Unfortunately there is no connection between XTU and DPTF and there is also no straight TDP configuration in DPTF registry entries (just something like if Power profile x is set and AC or DC – set TDP, cTDP high or cTDP low).

    Since I removed DPTF setting TDP configuration persists and throttling responds to PL1 up to 20W. Temperature is around 80°C with fan speed at least one step under max speed hence quite good margin to accommodate at least 25W what is cTDP high of i7-6600U (no one designs special platform for one of the processors in the line hence its logic it’s able to cool even 25W). Regarding i7-6600U I really don’t understand Intel designers and marketing – they add twice as much power hungry GPU cores to 6650U in comparison to 6600U but they limit maximum allowed power to 15W instead of 25W (CPU cores alone eats up to about 16W including uncore and GPU cores more than 22W) it’s really strange.

    Nothing is perfect. Once I switch from AC to battery CPU throttling stops responding to TDP configuration and keeps it on default 15W until I switch computer off, on and suspend/resume again. But anyway it’s clear TDP is programmable under specific circumstances. Is anybody who wants help me discover more or at least guide me where to find useful documentation? Intel publicly available documentation is high level covering just functional description nothing useful…
     
  2. Dufus

    Dufus .

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    Intel are pretty good at keeping secrets. A BIOS writers guide would help a lot but that requires NDA as do a lot of other docs, never seen one myself in all my years. :(

    Coreboot and linux source code can find some useful info but most if it comes empirically derived without doc's which usually takes time but things can be learned that perhaps don't even exist with NDA. For power management an understanding of the embedded controller would help a lot however they tend to be not so generic with firmware. Finding EC IC data sheets which are likely different for different machines would be beneficial.
     
  3. Meschrenz

    Meschrenz Newbie

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    Hi everybody!
    I have laptop Acer Aspire E1-570 with core i3 3227u CPU.
    I have problem with my intel hd 4000. So, it use only 350 Mhz when AC power plugged in. But from battery it is boosting to 1100 Mhz. And from battery package power is 20 W, but when plugged in maximum is 7-10W.
    I think it is either power throttling or intel hd frequency throttling.
    Temperatures is OK, I changed AC adapter too.
    Acer and Intel forums sent me here.
    Can u help me with this thread?

    You can find more information here: https://communities.intel.com/thread/110488
     
  4. D2 Ultima

    D2 Ultima Livestreaming Master

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    I recommend making a new thread entirely about your problem. I suspect the issue might be in some windows settings, though.
     
  5. Meschrenz

    Meschrenz Newbie

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    Windows and Intel forums gave me link to this thread...
     
  6. D2 Ultima

    D2 Ultima Livestreaming Master

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    Yes, but you've revived a rather old threat that fewer people will click on. Just make a new one in the hardware/upgrades forum.
     
  7. psil0

    psil0 Notebook Enthusiast

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    Hi guys Im having Power limit throttle issues and maybe you guys can help. It happens when TDP package passes the limits that are locked. I want to unlock them but my BIOS is super simple and I can tweak almost nothing. Using HWinfo32 shows:

    CPU Thermal Design Power (TDP): 47.0 W
    CPU Thermal Design Current (TDC): 85.0 A
    CPU Power Limits (Max): Power = Unlimited, Time = Unlimited
    CPU Power Limit 1 - Long Duration: Power = 47.00 W, Time = 28.00 sec [Locked]
    CPU Power Limit 2 - Short Duration: Power = 58.75 W, Time = 2.44 ms [Locked]

    So i can set the power limits to an unlimited value, but it seems the manufacturer locked the limits.
    How can i unlock them??!!!

    Thanks,

    I have a clevo n170sd:
    HM87
    i7-4720HQ
    GTX960M
    8GB DDR3 1600mhz
    windows 10 pro
    AC 120W
     
  8. psil0

    psil0 Notebook Enthusiast

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    Hi I'm having Power limit throttle issues and maybe you might help. It happens when TDP package passes the limits that are locked. I want to unlock them but my BIOS is super simple and a can tweak almost nothing. Using HWinfo32 shows:

    CPU Thermal Design Power (TDP): 47.0 W
    CPU Thermal Design Current (TDC): 85.0 A
    CPU Power Limits (Max): Power = Unlimited, Time = Unlimited
    CPU Power Limit 1 - Long Duration: Power = 47.00 W, Time = 28.00 sec [Locked]
    CPU Power Limit 2 - Short Duration: Power = 58.75 W, Time = 2.44 ms [Locked]

    So i can set the power limits to an unlimited value, but it seems the manufacturer locked the limits.
    Is it possible to unlock the limits??!!!

    Thanks,

    I have a clevo n170sd:
    HM87
    i7-4720HQ
    GTX960M
    8GB DDR3 1600mhz
    windows 10 pro
    AC 120W
     
  9. Nep Nep

    Nep Nep Newbie

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    I had the same problem with my Alienware 17r2 but the AO9 bios does allow me to change it easily.

    I have the exact same processor.

    I assume you've tried looking for bios updates?

    Incidentally... increasing my limit to 72 watts from 47 didn't do a thing.

    I tested it by playing Assassins Creed Black Flag, running around the intense jungle areas and power limit throttling would still occur.

    Try these settings in Throttlestop.

    http://forum.notebookreview.com/threads/early-2015-throttling-some-info-id-like-to-share.787044/

    Don't forget to get rid of Intel Dynamic thermal framework.

    I haven't tested them fully myself but they stopped the power limit throttling that was occurring in Skyrim Special Edition for me.

    I'm gonna test more games though to see if it really holds.

    Honestly I'm losing hope. I'm not even sure if I'll go with Intel next time cause of this. It's awful.

    I'm already too poor to afford more than this laptop for gaming, my primary hobby mind you... and it won't even hold it's turbo speed.

    I'm really hoping what that guy discovered in the thread works for my other games too.

    ---------------------
    EDIT -

    I gave those Throttlestop settings a go and they worked... I played Black Flag for a bit over an hour and the CPU never dropped below 3.2 GHz, I did have some thermal throttling but I haven't cleaned in there for a while and I really need to get around to removing the garbage stock thermal pads and put some high quality paste.

    I left my wattage at default just like their settings. As I've said before, changing the wattage doesn't seem to help anyways.
     
    Last edited: Feb 7, 2018
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