MBP '11 throttle CPU while doing something GPU intensive? Power requirement related?

Discussion in 'MacBook Pro' started by nnoob, Jul 5, 2011.

  1. nnoob, Jul 5, 2011
    Last edited: Jul 7, 2011

    nnoob macrumors member

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    #1
    I have done a few experiment on why some games like team fortress 2 keep dipping in fps.. I was convinced it was a CPU bound issue but after a few hours of investigating the issue, I ran Furmark and prime 95 together. CPU quickly from 2.2 ghz throttle down to 800 mhz and alot of 3d app does the same thing from (2.2 ghz to 1.x ghz) then when I close furmark then it instantly goes back to 1.9 ghz
    See screen shot for proof

    Please tweet this, reddit this, Facebook this,
    Make Apple aware of this issue!

    http://i.imgur.com/fzUfa.jpg

    http://i.imgur.com/64eOc.png

    EDIT:
    I tested it, it is not heat related! It the power requirement, I Turned off Wifi and disabled the LCD Monitor & plugged in external lcd .
    I am using the same program and same tool like the last one.
    http://i.imgur.com/etls3.jpg

    TL;DR: Any GPU usage will cause throttle on the CPU because insufficient power requirement?
     
  2. simsaladimbamba

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  3. maflynn Moderator

    maflynn

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    #3
    Do you see this in windows only, or OSX as well. The screen shots provided are windows.
     
  4. nnoob thread starter macrumors member

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    #4
    I think it applies to both platform, I am seeing similar in frame rate on mac source engine games. One guy here reported the same thing in WoW ..
    I believe he is running OSX version of WoW
    http://forums.macrumors.com/showthread.php?t=1181978
     
  5. fat jez macrumors 68000

    fat jez

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    #5
    If you think about it, you've picked two apps that will stress the hell out of your CPU and GPU and generate maximum heat. The heat sinks for both GPU and CPU are connected on the MBP, therefore if one of those is getting hot, the other will by conduction of heat too. Both CPU and GPU will have a maximum safe temperature (for the CPU, it's about 100°C) and once they reach this temperature, they will start to throttle themselves back until the temperature drops below a safe level. For effective cooling, you want to transfer from a hot item (CPU/GPU) to a cooler item (heatsink), but if the heatsink is already hot, the transfer will be minimal and the CPU or GPU will not be cooled as efficiently and the heat they are generating will not be conducted away as efficiently (hence their temperature increases).

    To cut a long story short, Apple didn't design the heat sink and fans in the MBP to cope with both the CPU and GPU generating maximum heat and both will throttle back to keep their temperature below danger levels.
     
  6. maflynn Moderator

    maflynn

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    #6
    Dumb question do you see the fan speeds ramping up as the temps increase?

    I'm guessing that the CPU is throttling down due to extreme temps. On my 2010 MBP, I notice that the temps increase from time to time without the fan speed keeping pace. I now run smcFanControl so I can I increase fan speed and thus keep my temps at a decent level.
     
  7. nnoob thread starter macrumors member

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    #7
    Yes, it ramp two fan to 6200 RPM. I checked it with SMC command line tool for windows.
     
  8. nnoob, Jul 5, 2011
    Last edited: Jul 5, 2011

    nnoob thread starter macrumors member

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    #8
    Any app will do the same, No matter what app you pick. Why would apple put a core i7 quad core and AMD Radeon graphic knowing they can't handle the "heat" requirement. I paid $2000 for a premium laptop. I would love to see apple address this "issue" in a uEFI BIOS update.
     
  9. fat jez macrumors 68000

    fat jez

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    #9
    an EFI update is not going to have any bearing on how well the heat sink and fan combo in an MBP cools. The example that you picked is to choose two apps that are known to generate maximum heat on CPU and GPU and run them together, it's hardly surprising in a laptop solution that the CPU had to throttle back to keep itself under a safe temperature. It's either that or it would die a death due to overheating.
     
  10. nnoob, Jul 5, 2011
    Last edited: Jul 5, 2011

    nnoob thread starter macrumors member

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    #10
    My point is this: Then why most 3D app run at 1.x ghz instead of 2.2 ghz. Like for example Team fortress 2 & CounterStrike Source at ~1.6 ghz.. and a app that runs at 11,000 FPS while running a single thread prime 95 at ~1.7 ghz

    these app are not heat intensive (except for prime 95 single threaded)
     
  11. Mr MM macrumors 65816

    Mr MM

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  12. fat jez macrumors 68000

    fat jez

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    #12
    Any 3D app is going to heat up the GPU. The heat from the GPU passes into the heat sink. The same heat sink connected to the CPU, therefore the efficiency of cooling on the CPU is going to be diminished by having a warm heat sink. since the CPU is not being cooled as efficiently, it will start to over heat and need to throttle back to keep itself at a safe temperature.

    Oh and Furmark has been known to kill graphics cards on the PC with the amount of heat it generates and Prime 95 by default runs multi-threaded when stress testing.
     
  13. dagamer34 macrumors 65816

    dagamer34

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    #13
    AMD will throttle your video card when it detects an application like FurMark because it does not want you to destroy your GPU and have you complain to them. FurMark puts the GPU under more stress than would ever be seen in the real world, and as such, AMD doesn't support such uses.

    And it's a laptop for christ's sake. There's only so much cooling to be had in fans that aren't even an inch thick!
     
  14. ivsetiaw macrumors newbie

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    #14
    So, is this problem happening to everyone or just few of us? Is this something you really need to concern about? I also found this thing happening to me lately, even when my cpu is idling...
     
  15. 2hvy4grvty macrumors 6502

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    #15
    It's a wattage issue. Not enough power is being supplied when both GPU + CPU are being stressed.

    It's made worse by Intel's turboboost, which obviously isn't the most intelligent thing in the world. What basically happens is... apple designed a power supply that would provide enough power for both the CPU/GPU as per their TDP reqs. However, tb 2.0 basically OC's itself when it sees an overhead and therefore uses up more than its fair share of power.

    When that happens, the GPU is basically being starved. Seeing this, the intel downclocks itself to 800mhz (or whatever the idle step is nowadays) and that's the cause for the drop.

    Thing is, it's honestly present in most laptops on the market today <15 inch. And this isn't something Apple can release a "fix" for.

    What were you going to have them do? The battery can only output so much power in a given moment. The chemistry in batteries is a fixed commodity; not something you can change via firmware.

    If a full bore GPU and other components require more power than the battery can supply in a burst, I don't understand how they could have patched this in any other way. Suppose the MBP on full load takes about ~125W. If the battery can physically only supply 100W in a burst (I'm making that number up), I don't know where firmware was supposed to find 25W more. Magic? Unicorns? Downclocking/Throttling is the only solution. Sure the fixed 200 Mhz clock is annoying and something slightly higher would have been nice, but that doesn't solve a truly physical limitation of hardware.

    Don't understand how people can expect miracles out of battery technology that fundamentally hasn't changed in ages. Lithium Ion was initially conceived /researched in the 1970s...

    Basically, think of it this way, Acer's have throttling issues across their entire line under NORMAL use. Consider us lucky. But Acer's blow.
     
  16. fat jez macrumors 68000

    fat jez

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    #16
    Yes, but when that happens, it starts drawing power from the battery to make up the short fall. Neither CPU or GPU are starved of power.
     
  17. 2hvy4grvty macrumors 6502

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    #17
    Theoretically, Apple should be able to fix the issue when connected to power.

    But there's nothing they can do if you're on battery. Batteries are rated at a certain output, that's all they can physically manage. Unless Apple makes a recall on batteries, throttling will always exist in that field.
     
  18. fat jez, Jul 7, 2011
    Last edited: Jul 7, 2011

    fat jez macrumors 68000

    fat jez

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    #18
    I think you mis-understood what I wrote. If the power supply is not able to supply sufficient power, the MBP starts drawing on the battery to make up the short fall. There are threads on here about people whose batteries were draining whilst plugged into power.

    http://forums.macrumors.com/showthread.php?t=1163889

    However, I don't believe that either CPU or GPU will throttle under those circumstances, only when they get too hot.
     
  19. 2hvy4grvty macrumors 6502

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    #19
    Well, from my understanding, if you hit the thermal threshold on either components (105 for the CPU, no idea for the GPU), the laptop would shut down, not throttle. No CPU should "throttle" with heat; that'd be a large cause for concern.

    If you're driving and you're about to hit another car, you'd slam on the brakes, not ease off the throttle.

    Anyway, easy way to test is to measure the power draw and compare it to whatever the battery's rated at.

    Also, just so we're clear, the CPU/GPU/HDD/anything can only draw power from the PSU, not from the physical batteries itself. The battery powers the PSU. The there are no connectors running from the battery... to the CPU/GPU.
     
  20. fat jez macrumors 68000

    fat jez

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    #20
    You're going to be busy then, educating a lot of people about how their CPU doesn't throttle when it gets too hot, as there are a LOT of hits on Google about it.

    The CPU will throttle back to a lower clock speed when it gets too hot. Then and only then if it is still too hot will the machine initiate a shutdown.




    So explain to me how the power goes to the CPU, GPU, logic board, drives, etc? If you take your laptop apart, you will see there is a connection from the battery to the logic board. This is in addition to the connection from the Magsafe connector. Both will supply power if power from the adaptor going to the logic board is insufficient.

    Go and read that thread I linked to where the guy has a battery that discharges while gaming, despite plugging his laptop into the mains electricity supply and then come back and explain to me how he losing power.
     
  21. 2hvy4grvty, Jul 7, 2011
    Last edited: Jul 7, 2011

    2hvy4grvty macrumors 6502

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    #21
    Cheers mate, good looking out. I was thinking desktop terms: outlet -> PSU -> which provides the connectors. Seems things are a bit different if that's the case. This makes me curious.

    Will post with edit.

    Also, at what temperature does throttling occur? Because I hear people hit 95c under use...

    EDIT: Wait, I just realized that's the same thing. PSU in this case IS the battery (there's no battery in desktops). It provides a limited amount of power. My semantics were a bit off, point still stands. lol it'd be pointless to have a battery that does nothing but connect itself to a PSU, which also does nothing but connect itself to the mobo.

    Battery power is rated at a certain watt output. When that watt output is exceeded (and it will), where would that extra power come from? You can't just put in a couple lines of code and change the entire chemistry of the damn thing.

    And I don't know why you're bringing the wall adapters into this. I did say that was a possible fix if that's the problem. I'm merely pointing out that while on battery power, you'll experience throttling underload, and that's not something Apple can realistically fix with software.

    Also, this is just speculation based on my understanding of hardware, combined with any facts I can find to support/debunk the idea. There's no need to get on my case about it. It's not like I'm AGAINST apple fixing it.

    @teaching people: I'm not out to change the world. I do what I do. Most people are ignorant, that's fine. They do what they do. There a bunch of lies out there that only the most informed individuals would know. I'm just throwing out a couple here: dynamic contrast ratio is almost a completely worthless statistic; higher VRAM rarely means more FPS, because the bottleneck is almost always elsewhere; the importance of CPU cache vs clock speeds; CPUs on a nano-level (the transistor architecture) vs raw clock speeds. There's obviously no point in teaching everyone who's ignorant of these things, because quite frankly, most don't care.

    EDIT2: Now that I think about it, throttling could be a result of heat also. If it is, that's fixable easily.

    Can't help but wonder if battery's the cause as well, since power/current consumption are both factors.
     
  22. fat jez macrumors 68000

    fat jez

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    #22
    Depends on what T junction max is for a given CPU. According to Intel, it's 100°C for a mobile i7.

    http://ark.intel.com/Product.aspx?id=52227

    Once the temp hits this, the CPU will throttle. If the temp still exceeds this, it will shut down.

    I experienced this on my PC when my cat lay along the top of my case where the exhaust fans for my radiator are. The PC got slower as it throttled until it suddenly shut itself down. I was not impressed and now have to shoo her off the top of the PC if she sits there (it's beside my desk, not under it).
     
  23. 2hvy4grvty macrumors 6502

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    #23
    Ok, dug up some info. Some very basic math here (+common sense physics):

    Apple magsafe power rated at 85w (couldn't find anything on the battery, some help here?).

    2720QM rated at 45 w at full load.
    Only data on the 6750m I could find was "similar to 5770m" which was 30 w at full load.
    HDD ~5-6 w at full speed.
    RAM ~4-5 w.

    That maxes the magsafe already.

    The logic board itself should draw at least another 10 w. And there's that damn optical drive, which accounts for another 10w.

    Throttling because of lack of power is a very plausible theory and is unfixable by a mere "update".
     
  24. fat jez macrumors 68000

    fat jez

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    #24
    I give up. In a desktop PC, insufficient power leads to random crashes. In a laptop, it makes up the short fall from the battery.

    It's what happened to this guy in this thread.
    http://forums.macrumors.com/showthread.php?t=1163889

    Apple could resolve the battery issue quite simply by producing an uprated power brick, maybe running at 100W instead of 85W.
     
  25. 2hvy4grvty macrumors 6502

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    #25
    I think you're missing the point. I'm talking about if and when both components are being stressed while being powered by JUST the battery, throttling can't be helped.

    I understand what you're saying, you can stop linking me to that thread now. You're saying power draw exceeds what either the battery/magsafe can provide, so it "makes up" for it by drawing power from both. Ok. That's fine.

    But I'm saying, throttling when caused by lack of power will ALWAYS occur when one is running solely on the battery. You can't just "complain to Apple" and expect it to be resolved. Connected to power? Yeah, that's fine. Larger power brick, simple. It's the equivalent of getting a brand new PSU on the desktop analogy. That's a easy fix.

    But short of a battery recall (not happening), we're stuck with throttling while gaming/whatevering on battery. Apple can release all the updates it wants to tell the mobo to "draw more power", but the battery isn't going to listen. It does what it does.
     

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