CPU 45W TDP Limit

Discussion in 'Hardware Components and Aftermarket Upgrades' started by Danishblunt, Nov 21, 2017.

  1. Danishblunt

    Danishblunt Notebook Virtuoso

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    So I started an interesting discussion with @hmscott , he claimed that apparently there is a 45W TDP limit in his notebook, which I simply cannot experience in mine.

    So I decided to make this thread in order to figure out if either hmscott does something wrong or if indeed some notebooks out there are indeed limited for some reason.

    So if you would participate in this experiment do the following:
    - Download XTU and setup your CPU
    - Config ur CPU to good performance
    - Run some kind of benchmark, XTU benchmark should be fine, monitor your TDP W.
    - Also Monitor your Benchmark while having HWinfo64 on to see min and max wattage etc.
    - Post a screenshot like this one below:
    - Provide your notebook model
    [​IMG]

    According to hmscott, it seems that his CPU gets locked to 45W TDP when his short turbo is running out, implying that his notebook is overwritting his limit which he set on turbo boost to 45Watts, which is interesting, since if that's the case that would mean that some notebooks restrict overclocking.

    I hope to see some results!
     
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  2. hmscott

    hmscott Notebook Nobel Laureate

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    Demystifying how Intel-based mobile Core i7 processors work: Clocks, throttling and thermal performance explained.
    https://gist.github.com/Brainiarc7/fc7e24f8bbd0336b2cf796e89800e3e8
    ...
    Second, you can run out of power (watts/TDP), referred to as power throttling. This is was usually as a result of an inefficient power adapter, being on battery, or simply the motherboard of the laptop not allowing enough power to be fed to the chip (either by a physical limitation, or by not allowing the turbo boost power limit to be increased), however to date all HQ chips (the only chips intel is using anymore) throttle to their default long power TDP (usually 45-47W) after a couple minutes (more on that below). If this is your issue and buying a bigger power adapter (assuming one is available) does not fix it, then buy a better notebook (or one of Clevo's desktop-CPU-using notebooks if you have a HQ chip).
    ...
    Intel Core i7 49xxHQ/5950HQ variants: Increasing the TDP limits and amperage, etc via the BIOS or XTU DOES actually work for these chips. Confirmed using both Alienware and MSI notebooks. The problem however, is that the CPUs only keep the higher power limits for approximately 2 and a half minutes, just like with the 47xxHQ chips. This is more than enough for most benchmarks however, as anything that doesn't cross the base power consumption for the CPU will hold (such as GPU-heavy parts) and the parts that stress the CPU are usually ~1 minute long at most. When under serious load in gaming, however,these chips are not for you. They're not going to hold their clocks (likely not even stock, unless you seriously under-volt) under extended load times.
    ...
    Intel Core i7 6700HQ chips: No clock adjustments are possible (even turning down turbo boost seems impossible in tested machines; you WILL have 3.5GHz 1-core, 3.3GHz 2-core, and 3.1GHz 3-core and 4-core turbo, or you disable turbo entirely). There is no manual adjustment possible and no free +200MHz overclock granted. I do not know whether it holds its power limits or not, as all laptops tested have either overheated before breaking the power limits, or simply couldn't hit the power limits whatsoever. I have no idea whether this CPU can hold over its in-borne TDP limit under load, and I suspect that I will both never know, and also that it will never matter; you're probably not going to draw enough from this slow chip.

    Speaking of slow, remember that this chip is a 3.1 GHz 4-core turbo lightweight. Every single standard Haswell mobile SKUs, not including the ULV parts (I.E. ignore the 4702HQ and 4712HQ), if working properly, are at worst, equal to this chip. If you have one of those machines already, this is not an upgrade, and is most likely a downgrade, unless your current chip cannot hold its turbo clocks for some reason."

    The Haswell test that you posted showing 2 minutes of high power draw is not long enough, you need to run for at least 5 minutes, and I'd like to see a 15 minute run. :)

    And, see my last post to you from the closed thread for additional XTU graphing to show package TDP, thermal and power throttling.
     
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  3. aaronne

    aaronne Notebook Evangelist

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    Last edited: Nov 21, 2017
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  4. Danishblunt

    Danishblunt Notebook Virtuoso

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    Thanks for the read and link!
    My theory is hereby confirmed then.

    Guess u gotta find yourself a modded Bios to get it from stopping to nerf your CPU over time :p

    However this is so expected from Alienware:
    So from what I can gather from that nice post was the following:
    - MQ models apparently have no problem going beyond the limit.
    - HQ models do have this set limitation, however can be fixed with a modded BIOS
    - XM/MX models do not have this limitation and can go beyond as well.
    - 6700HQ is inferior to older ivy and sandy bridge CPU's due to hard nerf.

    In a nutshell, manufacturers nerfing their CPU so that people have a reason to buy next gen. Also Alienware is the pinnacle of disapointment.
     
    Last edited: Nov 21, 2017
  5. bennyg

    bennyg Notebook Deity

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    What notebook? P157SM iirc?

    Protip: ignore what XTU says. It's unreliable. Go by Hwinfo or Throttlestop, especially for throttle and power limit reasons.

    I notice you have cTDP there... that popped up when I installed the 3940XM in my P370EM. It wasn't there with the QM CPUs. It would keep setting a 81.25W short power and 65W long power limit, I have to override this every boot and resume with a XTUCli script setting them to 95W/90W which allows 4.5ghz.

    Your package power (TDP) seems to be suspiciously close to 65W, too... and what are the other limit/throttle readouts on HWInfo? It looks like your CPU IS throttling for various reasons...

    Stress tests that show you the work being done can show up throttling. 7zip benchmark is a weak one but consistently shows MIPS. Intel Burn Test is a cycling stress test, it'll show GFlops and will show up any power limit you got.
     
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  6. Danishblunt

    Danishblunt Notebook Virtuoso

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    My CPU doesn't throttle (as seen on the image), it makes sense that it's only around 65W considering it's "only" 4ghz and the voltage is 1.065. Also the "throttle" you're refering to is a 2-3mhz dip caused by AMP limit. I only have it on 90, should have had 100. (as far as I know throttle means if it dips below clock speed or it thermal throttles because of thermal, so I think the term "unstable" is much better suited rather than throttle since it does seem to mean something different.)

    HWinfo reports no throttle at all (hilariously enough XTU does report AMP throttle limit EDIT: Looking at power limit exceeded on my previous, It seems that AMP limit is meant with that, so HWinfo does report a limit problem on my 90AMP setting.)

    I can make another test if you want to see a straight line with 100AMP limit :)

    EDIT:
    Here it is:
    [​IMG]

    not a single mhz dropped, 100AMP limit did the trick ;)

    Also yes, it's my P157SM.

    @hmscott
    Ur article says 2.5 mins.... Well still here u got a 6min stresstest :x
    I can tell you 100%, that this notebook does not limit my CPU in any way shape or form after any time, I play games like Mafia 3, Witcher 3, Dota 2 which all are more CPU heavy and not a single time did I see anything else than 3990 on my MSI afterburner On Screen Display, ever.

    Also I really should fix the temps, looking at 90s makes me sad.

    So if the article is correct, then this means that custom BIOS are a must for anyone who can overclock their CPU.
     
    Last edited: Nov 21, 2017
  7. Vistar Shook

    Vistar Shook Notebook Deity

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    I don´t understand what the issue is, since the 45W TDP limit dos not apply to the i7-4940MX.
     
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  8. hmscott

    hmscott Notebook Nobel Laureate

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    Thanks for point that out, it's been a long circle of trying to turn him back to the locked CPU's, that's the subject of the previous thread, he doesn't seem to realize the power boost and TDP limit details are different for locked and unlocked CPU's.

    It's the 7700HQ that @Unhappy User had with his Turbo Boost Timeout Window set to 0.25 seconds and I suggested he use XTU to increase that to the maximum. I was hoping that would improve his CPU performance.

    Then it just kinda spiraled down from there... :)
     
  9. Danishblunt

    Danishblunt Notebook Virtuoso

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    That's what I was wondering about, since hmscott claimed that mobilechips are limited to 45W TDP, thanks to his article it seems that this is actually a microcode related problem and is mostly affected by HQ models, meaning even MQ models do not seem to face this issue.

    This is massively interesting since some people might have the situation where they consider either a HQ or an MQ chip. For instance @hmscott can Overclock his CPU rather nicely, but due to the microcode in his BIOS he is not able to use the full potential, which means that if he can get hold of a custom BIOS that fixes the microcode, he will be able to get rid of his limit set by the BIOS.
     
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  10. hmscott

    hmscott Notebook Nobel Laureate

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    It's the HQ CPU TDP power limit, not the BIOS, although there are power limits there too, as it doesn't allow more than about 62w CPU package power for that laptop, even when setting the upper limits to 200w.

    If you have an unlocked CPU, you don't have that HQ locked CPU power limit that's built into the HQ CPU. No matter how high you set the Power Boost or Short Power Boost, once that Turbo Boost Time Window expires, it drops down to the 45w or whatever TDP limit that HQ CPU has.

    That's why @Unhappy User running a 7700HQ with 0.25 seconds on the Power Boost Time window makes no sense, you want to have the longest duration in seconds possible, because once it expires your power is limited in the HQ CPU to the TDP set by Intel, 45w in that case.

    You were applying the unlocked CPU tuning to a locked HQ CPU, and that doesn't map over correctly. :)
     
    Last edited: Nov 21, 2017
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