imac 2011 27" CPU permanenttly works on half of frequency

Discussion in 'iMac' started by ed101utf8, Jul 10, 2016.

  1. ed101utf8, Jul 10, 2016
    Last edited: Jul 11, 2016

    ed101utf8 macrumors newbie

    ed101utf8

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    #1
    Hello everyone!

    I encountered with problem and I have absolutely no idea how to resolve it.

    I have an iMac mid 2011 27" with core i5-2400 (3100MHz) radeon 6970-1gb HDD 1TB .

    [​IMG]

    My HDD had broken, so i decided to install SSD instead of it. So I replaced old hard disk and put ssd Crucial MX200 500Gb instead. I installed Mac OS 10.7 from scratch using embedded recovery system, and after what updated to 10.11.5.

    Everything was fine until I decided pass some benchmarks. And all benchmarks show that cpu results only a half of expected. E.g Cinebench R15

    [​IMG]

    I tried to figure out what the problem and install Intel Power Gadget utility.

    It reveals next - CPU frequency does not rise higher than 1600MHz even in 100% cpu load tasks. It freeze on 1.60GHz a not move even a bit. The line on the graph is absolutely flat!

    [​IMG]
    And there are no CPU overheat as all! Temperature not raises more than 50C degrees.

    And GPU also work at ~20% of it power according to benchmarks (two times less points than ge-force 620m has).

    I have no idea how to resolve this issue. Please share your experience in such cases
     
  2. MCAsan macrumors 601

    MCAsan

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  3. Hellhammer Moderator

    Hellhammer

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    #3
    Have you just tried simple SMC and PRAM resets?
     
  4. ed101utf8 thread starter macrumors newbie

    ed101utf8

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    #4
    Yes, i tried. Didn't help :(

    What is it?
     
  5. maflynn Moderator

    maflynn

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    #5
    Basically, take it to an apple store, if you have one near you, otherwise call apple and schedule a pickup so they can work on it.

    The issue sounds like a hardware problem that you need them to work on.
     
  6. ed101utf8 thread starter macrumors newbie

    ed101utf8

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    #6
    Unfortunately we have not official Apple service in our country :(.
    Should I call apple or I can communicate in text mode? English is not my native language.

    I revert hdd on the initial place and install ssd as a second drive according to OWC video. HDD is not completely dead, it still can be used for multimedia files store, but os x can not boot from it. Seems to me hdd has some bad sectors.

    I did it because than I had changed ssd on hdd, occurred issue with 100% fan speed. I installed speed fan tune tool to resolve this problem. Nevertheless, reverting hdd didn't help, throttling problem still present
     
  7. maflynn Moderator

    maflynn

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    #7
    Where ever you bought the mac - give them a call.
     
  8. T'hain Esh Kelch macrumors 601

    T'hain Esh Kelch

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    #8
    What is the temperature of the CPU under load? And is the throtteling occouring right away, ie. before the CPU heats up?
     
  9. omvs macrumors 6502

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    May 15, 2011
    #9
    Did you use one of the thermal sensor cables when you swapped out the stock HD, or are you using a software program to control the fans? (Update - just saw you're software controlling the fans)

    When I had broken the LCD cable on my 2011 model, I just used it with an external monitor for a while, but I noticed the performance had tanked - can't remember if it was GPU or CPU, but it was quite noticeable in games. My suspicion is the system went into a degraded mode since some of the sensors wasn't working to prevent overheating.

    Might be worth the investment to get the cable - here's one example: https://www.google.com/url?sa=t&rct...SrgVYaDeX-IdXgdag&sig2=HrqwTVFbrviRiHv9ZUxFXg
     
  10. ed101utf8, Jul 11, 2016
    Last edited: Jul 11, 2016

    ed101utf8 thread starter macrumors newbie

    ed101utf8

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    #10
    This is screen of 100% cpu load:
    https://s32.postimg.org/npa8t9bhx/Screen_Shot_2016_07_10_at_13_22_19.png

    I can make it even 40C degrees - if increase fan speed to 100%
    --- Post Merged, Jul 11, 2016 ---
    There are no external temperature sensor for hdd, it embedded in hdd (hdd with some special firmware from apple). That's why i put hdd back and for now have installed two drives - original seagate 1TB HDD and SSD Crucial MX200. But this didn't resolve cpu frequency problem
     
  11. omvs macrumors 6502

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    #11
    Sorry, missed that part. Have you run AHD yet (Apple Hardware Diagnostics) -- it will tell you if any of the hardware sensors aren't working. I know when I took mine apart it was not uncommon to have to open it back up again since I hadn't had all the cables attached correctly...

    For that model I believe its on the applications CD, though if you don't have a {working} cdrom you can find AHD on the web and install it to a USB flash drive.
    --- Post Merged, Jul 11, 2016 ---
    Not related to the main issue, but I would recommend getting one of the cables with the thermal sensor and replacing the hard drive (or using a hard drive with the right firmware, but those are hard to find cheap). If the drive is just giving bad sectors its probably okay to leave it, but if the controller is throwing errors onto the SATA bus it could affect the system in other ways.

    A friend had a fusion setup in his 2011 27" which we unfused when the hard drive died. But the dead drive was still causing issues (long boots, maybe even crashes), so we pulled it and put in a third party + the sensor cable. Worked great - no fan problems or performance issues.
     
  12. kiwipeso1 Suspended

    kiwipeso1

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    #12
    I have this exact model of iMac, except with 16GB ram.
    This model has an unique HDD cable that has a specific heat sensor that automatically slows down the mac if the HDD is too hot and turns on the fan.

    What you need to do to fix the problem is put the SSD on the second drive slot, not the original drive slot.
    If you can get an Apple HDD to attach to that specific HDD cable, do that, but do not attach anything else to it.

    Just switch over which drive slot you use for the SSD, and only use the original drive slot for an Apple HDD with the right cable connections. (I think it is a single extra connector on the Sata cable which is not standard.)
     
  13. ed101utf8, Jul 11, 2016
    Last edited: Jul 11, 2016

    ed101utf8 thread starter macrumors newbie

    ed101utf8

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    #13
    There are two sata slots for hard drives on logic board. You mean they are different and i could attach ssd to initial hdd slot, and original hdd to second empty sata slot ? That's the point? I thought those slots are equals. Will try at evening, thx for your advise.
    --- Post Merged, Jul 11, 2016 ---
    I made some photos due installation
    [​IMG]

    [​IMG]

    Now ssd plugged into the same port as ODD (middle and right ports on the bottom photo). And original hdd plugged into left "separted" port. But it still not resolve my problem (
     
  14. omvs macrumors 6502

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    #14
    BTW - I believe the optical drive port is 'slower' (SATA2) so ideally you want to use one of the other ports for it.

    I'd re-iterate running AHD - it should tell you which (if any) sensors its having problems with if thats the case. Post the code it reports if it is not clear...
     
  15. kiwipeso1 Suspended

    kiwipeso1

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    #15

    No, that is exactly the wrong thing to do.

    The Original HDD goes on the unique cable with heat sensor so that the fan stays working correctly, and silently.
    The second drive slot is for the SSD, as that slot works with anything. (It doesn't have a special cable.)

    All you need do to get your iMac working correctly is swap the SSD from the Original HDD slot to the second drive slot which was empty.

    If you want to have a HDD in the original HDD slot, it needs to fit the special cable (which controls the fan and the issue you have with speed.)

    The original HDD cable is not equal to the spare drive cable, which is the thing causing the problem.
    --- Post Merged, Jul 11, 2016 ---

    Yes, the DVD writer (Superdrive) is on Sata 2. But the iMac 27" 2011 has two Sata 3 slots, of which the original HDD slot uses a special cable with heat sensor. It is capable of running entirely on a SSD in the second (spare) slot, as I had installed on mine.
    The issue with the special cable means it only works with the specific Apple HDD.

    To resolve the thread starter's problem, they need to put the SSD into the spare second slot
     
  16. ed101utf8 thread starter macrumors newbie

    ed101utf8

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    #16
    kiwipeso1, omvs, thank you. Looks like you were right - its thermal sensor:
    [​IMG]

    Now i have to disassembly imac one more time and try to understand that is wrong
    --- Post Merged, Jul 11, 2016 ---
    [​IMG]
     
  17. omvs macrumors 6502

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    #17
  18. ed101utf8 thread starter macrumors newbie

    ed101utf8

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    #18
  19. omvs macrumors 6502

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    #19
    Yeah, seems doubtful to me you'd be able to plug the wrong cable into that spot, or somehow swap with one of the other cables - they're nowhere nearby.

    I wonder if its actually the LCD proximity sensor and the google search results were wrong. The LCD proximity is on the same cable as the LCD data, and that cable is somewhat flimsy in my opinion. On the other hand, seems unlikely that it would get damaged without knocking out the data. I'd inspect the pins of the cable and see if they're okay - at least a replacement cable isn't terribly expensive if that's it.

    I believe when a sensor is non-functional the temp read programs won't show it. Do you see that ambient or lcd proximity is missing in the list?
    --- Post Merged, Jul 11, 2016 ---
    The 2009 model referred to in the post you mentioned is significantly different than the 2011 model. Here's a thread that corresponds to yours: http://forums.macrumors.com/threads...ilure-after-installing-another-drive.1710571/

    Hard to tell, but it sounds like you're looking at the right sensor cable... Not sure what to recommend.
     
  20. ed101utf8, Jul 12, 2016
    Last edited: Jul 12, 2016

    ed101utf8 thread starter macrumors newbie

    ed101utf8

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    #20
    Istats shows all sensors, LCD proximity too:

    [​IMG]

    If some sensor damage, will it shows in list?

    --- Post Merged, Jul 12, 2016 ---
    When I installed ssd, I also had replaced logic board and changed thermal interface on gpu and cpu. So probably i ruined something there. I will disassemble imac one more time and will try to understand that is wrong.
    --- Post Merged, Jul 12, 2016 ---
    kiwipeso1, could you please make screenshot of list of sensor on your imac? I wound be appreciated.
     
  21. omvs macrumors 6502

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    #21
    I realized the ifixit guide i sent was for the 2009 model, so what it labels the ambient sensor may be completely wrong.

    So I dug out the service manual - it states TA0P is definitely the ambient sensor, and that its connected to the left edge of the logic board, right above the left memory slot.
     
  22. kiwipeso1 Suspended

    kiwipeso1

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    #22
    That's correct, the 2011 model was unique with the additional HDD sensor.
     
  23. Gurpartap Singh, Jul 16, 2016
    Last edited: Jul 16, 2016

    Gurpartap Singh macrumors newbie

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    #23
    I reported the same problem back in 2014 when I added a SSD to my 2011 27'' iMac


    I
    never found a definite solution for the performance throttle. I used Macs Fan Control app to control the fans.

    I also saw a drop in gaming FPS, which I attributed to GPU being throttled at that time. Never thought CPU was throttling too until now.
     
  24. kiwipeso1 Suspended

    kiwipeso1

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    #24
    I had my SSD installed at an authorised repair centre, who have 25 years experience with Apple repairs.
    They did not touch my HDD, and simply installed the SSD in the spare drive slot.
    All that I have had to do, is change the default startup disk to the SSD, and it boots reasonably fast compared to the HDD.
    If I want to be pedantic, I can still use the HDD for an ultra fast time machine.
    However, as it is always on for a webserver, I leave it as a spare old system in case of failure of the current system.
     
  25. lakriz macrumors newbie

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    #25

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