Looping FPS drops every 6 seconds?!?!? even in MENU!?

Discussion in 'iMac' started by Rojoyinc, Oct 24, 2014.

  1. Rojoyinc, Oct 24, 2014
    Last edited: Oct 24, 2014

    Rojoyinc macrumors newbie

    Sep 13, 2011
    Ive been going crazy trying to track down the reason. I have a iMac i5 3.1 mid 2011. With AMD 6970M 1gb graphics card.

    When I got this machine (it had Lion) and graphics games (3D) ran fine. I use to run F1-2012 in max res - all settings on high and ran great ALL games ran great.

    Recently I noticed a STRANGE (as in not related to graphics intensive issues) games running FAST (50 - 60fps) for 6 seconds. But then stutter down to about 12FpS for 2-3 seconds. This is a loop - which has nothing to do with what the game is doing. It will do it in a 3D game menu for example. Or not moving in a 3D game and just looking at the floor.

    The problem I thought at first was (just that game) so I don't recall when it started. Later I noticed it's all 3D games. The only changes have been. (updated to Mavericks, then more recently Yosemite and problem persists. Could the update in OS cause this?

    What is what I'm getting. I thought it was this game only, but went back to try F1-2012 and it does that same thing and didn't use to at all!?!?
    I have 12GB ram, This happens in ALL GAME RES settings, but the frame rates will increase or decrease of course - but the LOOP persists. In highest res it might go from 6 seconds of 40fps to 2 seconds of 8fps. In lowest res I get the same - but say 6 seconds of 60fps and 2 seconds of 13fps. Both loop at the same interval!? If this is a hardware problem? I Wish I knew what - so I could get my repair shop to fix it.
    Image to small? link direct...



    Model Name: iMac
    Model Identifier: iMac12,2
    Processor Name: Intel Core i5
    Processor Speed: 3.1 GHz
    Number of Processors: 1
    Total Number of Cores: 4
    L2 Cache (per Core): 256 KB
    L3 Cache: 6 MB
    Memory: 12 GB
    Boot ROM Version: IM121.0047.B1F
    SMC Version (system): 1.72f2
    Serial Number (system): DCPH31A5DHJQ
    Hardware UUID: 8ABE5F3B-DAC5-5C77-A78F-5AFCD0CCDF89

    AMD Radeon HD 6970M:

    Chipset Model: AMD Radeon HD 6970M
    Type: GPU
    Bus: PCIe
    PCIe Lane Width: x16
    VRAM (Total): 1024 MB
    Vendor: ATI (0x1002)
    Device ID: 0x6720
    Revision ID: 0x0000
    ROM Revision: 113-C2960H-188
    EFI Driver Version: 01.00.544
    Display Type: LCD
    Resolution: 2560 x 1440
    Pixel Depth: 32-Bit Color (ARGB8888)
    Main Display: Yes
    Mirror: Off
    Online: Yes
    Built-In: Yes
  2. fisha macrumors regular

    Mar 10, 2006
    From a cold start - i.e. having left the computer off overnight, then booting it and going straight to the game ... does it do the looping immediately, or does the looping start after a few minutes of play.

    It could be something like the CPU/GPU is throttling its power due to heat issues. and its cutting back to cool down for a couple of seconds, then realises its cool enough, and throttles back up, heating up, then getting too warm. A cause may be that the heatsink is not getting a good contact etc ?

    I think you need to look at other CPU / GPU intensive tasks as well. It doesn't look like your hitting 100% CPU usage at any time. What about trying to encode/transcode a length of video? Does it loop then too?
  3. Rojoyinc thread starter macrumors newbie

    Sep 13, 2011
    WOW I think you're on to something. (and I have a smirk) because I had thought similar. But thought I was full of crap, so I didn't really pursue it. Also know I am running something called MAC FAN CONTROL. I had fans turned down (mostly HDD) because of the noise. (is this stupid to do? I'm a PC guy since the 1980's. Sold, serviced programmed - totally windows Guru. Until I got a Mac (given as payment of a job. I would have NEVER bought a Mac).

    a week later - I'm a MAC GUY and only revert back to the PC and windows when it's a must. BUT I'm a newbie Mac guy. I wondered about the fan, but only tested to the extent of going to the icon and clicking "EXIT" to kill the app. (assuming fan control would stop and it would just auto... take over). not sure if it did or if app stayed in background.

    My machine is on all the time, I allow the screen to go black at night. I usually download at night... (but not always) should I power down? Always left my PC's running.

    So I go to Fan control and instead of killing it, I set the CPU/heat sync to MAX RPM. 2600 I think it is. I could hear it pickup. Machine still (warm) been on all night and I tested the game. WAS FINE. Played fine no loop in speed for about 5 minutes. Then it started.

    I'm out of the game and watched the fan control temp. It was in the 90's and now it has settled to 86.7 F.
    I'm going to load the game and test right now. brb

    Game ran fine for 3 minutes started looping at 92.8

    I have a friend that has a iSTORE for all used Macs and services them. I can bring it in to him. (I got it from him for sign work). If he opens it - and the heat sink isn't loose? is there another option like adding a fan on it? or is the CPU over heating because it's going bad? any idea?
    What is normal operating temps?

    thank you SO MUCH for narrowing it down and confirming what I had considered, but didn't really take very seriously as I'm new to Mac's.

    I'm going to shut down, and test again from cold boot. I am surprised that the CPU cuts back at only 92.F but I really know nothing about CPU temps.


    What makes it throttle down? any way to circumvent that? or will that just burn out the CPU?
  4. fisha macrumors regular

    Mar 10, 2006
    I've personally never felt that the fans were that noisy on my 27, unless it was encoding for a long time. Under normal running I don't hear the fan. I've never used a fan control app and let the mac sort itself out.

    For a given design, the faster the CPU works, the more power it draws, the more heat it generates. Modern CPUs employ a number of power saving methods, a big one being to reduce its clock frequency ... The net result power wise is less heat ... So if the CPU is detecting that it's getting hot, then rather than melting itself to bits, it'll cut the frequency and see if that helps, once cool, it'll ramp back up again.

    But cooling inside requires air getting to it as we'll. is the iMac enclosed at all or it's vents blocked with dust? Is it getting to breathe basically.
  5. RyanJWilliams macrumors newbie

    Oct 18, 2014
    Considering that you've a background in servicing computers, you've been doing some pretty daft things.

    All hardware components for computers will eventually die, they age through use. Cooling is the one thing that stands between these components and their inevitable demise. By not allowing your components to enjoy the cooling that is optimal for them, you've almost certainly reduced their lifespan. The thermal paste on your CPU is one thing that's particularly vulnerable to wearing down over time, which will eventually prevent cooling.

    That aside, your computer has also probably filled up with dust — this is almost unavoidable unless it has dust filters on the inlets, and even then it still happens. This combined with the inadequate cooling has likely led to the temperature levels consistently being too high.

    Compounding all of this is the fact that you leave your machine on all the time. Not only is this a huge waste of energy unless you actually need it on, but you're also accelerating both the hardware ageing process and the dust increase described above.

    My advice: stop doing all of those things and tolerate the extra noise. You're well on your way to the end of your iMac, which I should point out is an extremely tightly enclosed machine that's known for often running on the edge of what is acceptable in terms of heat. Doing anything that compromises its already challenging cooling requirements is exceedingly unwise.
  6. Rojoyinc thread starter macrumors newbie

    Sep 13, 2011
    I have no dust. inlets on bottom are clear - as is outlet slot on top. Never had heat issues with my PC work in the past. (they're so open). the "ALL IN ONE" case of the iMac has always worried me.

    My iMac repair friend said it's not the heat sync. He said if it comes off which is nearly impossible, he said the cpu would fry. I'm not sure who knows more you guys or him. But he does make his living repairing Macs. I wonder if it's GPU related and not CPU. GPU doesn't have a fan I suspect? (I've not been inside a Mac). (yet).

    I did a cold boot - ran the 3D game and it ran fine for 5-6 minutes. I recorded the data at the start and after the problem started. See what you think of temps. Also if you download and run Mac Fan control (google it free app) you don't need to adjust them, it will read your temps even if you don't configure your fans to change from normal.

    Anything look out of line for temps?

    BEFORE problem.


    After the problem.

  7. RyanJWilliams macrumors newbie

    Oct 18, 2014
    The GPU is the most likely suspect. I have known very few CPUs to die in my time building computers, however I personally have had four GPUs die — each after two or three years, and all very expensive high-end AMD and NVIDIA units.

    I do run them pretty hard as I do both multimedia work and gaming. They'd probably have lasted twice as long for a less intense user. But they all die eventually, and like I say it's usually heat damage that leads to this. Even in a perfect environment, such damage occurs. It's just much slower.

    I suspect that in your case, your GPU is in bad shape following years of being left on all the time in an already pretty warm environment. It may not be repairable, but it's most likely replaceable. With a PC the first thing I'd do is swap in another GPU to see if it fixes the issue, but with Macs you pretty much have to let a repair shop do that unless you're brave and skilled.

    Your temperatures don't look super bad in those images, although it all depends on what the GPU's operating temperatures are rated at (this is usually in their specifications). But like I say, over time running at a relatively high temperature will take its toll regardless of moment-to-moment temperature.

    Perhaps there is some crazy software reason for all of this, which is what swapping the GPU would clarify. I'm not sure what to suggest for that though, unless your friend is willing to do it.
  8. Rojoyinc thread starter macrumors newbie

    Sep 13, 2011
    Solve the problem (kind of) I was running a app called Mac Fan control. Nice app you can set speeds of fans and even the HDD which is quite loud unless I turn it down. I think turning it down may allow it to get warmer? (is there a fan on a Mac HDD?) At any rate - I changed the setting in Mac fan control for the HDD from constant RPM value (which I had set about 3000) to barely hear it.

    I had maxed the fan settings for CPU - but didn't seem to be enough. When I put the HDD setting to "AUTO" It spins up (LOUD) and the 3D game ran for a couple hours without any slow down.

    I've just changed the setting to set the HDD according to GPU sensor. If the GPU heats up past 150 F it will increase speed. I'm booting from a SSD, the internal 2TB really doesn't get used. so I wish now I hadn't had that installed. (I use 3-externals 3TB) drives and the SSD. I imagine keeping the 2TB HDD out of the iMac would have helped keep it cooler inside.

    At any rate - I just got the Temp gauge app by tunabelly software to monitor things. I am a bit puzzled at being able to control the rpm speed of the HDD. I thought they were constant (on PC) and I've not seen a fan on a PC HDD. How can spinning it faster keep it cooler?
  9. RyanJWilliams macrumors newbie

    Oct 18, 2014
    Glad you fixed it. I don't know if the iMac has a fan positioned near the HDDs, sounds like it does. I'm using a regular PC that has a fan in front of the HDDs specifically for pulling air away from them, so it's certainly something that is done.

    I would still recommend that you don't mess around with the fans on your iMac. It's fine to do such things with spacious desktop computers, but iMacs are very much like laptops in that they're very carefully designed in terms of thermals, and by messing around with that you risk introducing early hardware failure. If an official repair shop knew you'd been doing this they'd probably turn you away.

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