Plan on 21.5" CPU Replacement to i5 760. Thoughts?

Discussion in 'iMac' started by pt0016, Nov 19, 2010.

  1. pt0016 macrumors regular

    pt0016

    Joined:
    Jul 9, 2010
    #1
    Hi there,

    What do you guys think of replacing a 21.5" 3.2GHz Core i3 550 CPU with the 2.8GHz i5 760 - the same ones as in the 27" iMac. I know the processor is socketed, and I'm willing to risk my warranty.

    Seeing as the iMac has some pretty beasty fans, I don't see heat being an issue, and the only issue could be the PSU suppling enough power?

    They both use the same sockets LGA 1156, and using this guide http://www.ifixit.com/Guide/Repair/Installing-iMac-Intel-21-5-Inch-CPU-Replacement/1859/14, I'm sure I can get the CPU replaced.

    This is what I plan on getting: http://ark.intel.com/Product.aspx?id=48496

    What are your thoughts on this?

    Cheers
     
  2. Hellhammer Moderator

    Hellhammer

    Staff Member

    Joined:
    Dec 10, 2008
    Location:
    Finland
    #2
    Nobody has tried this AFAIK so you would be our guinea pig. Heat shouldn't be an issue but your fans may run at higher speed and thus cause more noise. Since you have 3.2GHz i3, you have ATI 5650 in it so PSU shouldn't be an issue. It's designed to power 4670 which is 11W hotter than 5650 (aka 5730M), thus it should be able to power a beastlier CPU although it's 22W hotter (only 11W difference, PSUs are always designed to power a bit more and that's only under very heavy load)

    Can't promise that it works but can't see why not
     
  3. Bkxmnr macrumors regular

    Bkxmnr

    Joined:
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    Location:
    Wichita, KS
    #3
    Aren't the 21.5" iMacs Clarkdale only? Would it even recognize a Lynnfield processor?
     
  4. southbark macrumors regular

    Joined:
    Dec 15, 2006
    #4
    All LGA 1156 processors and motherboards made to date are interoperable, making it possible to switch between a Celeron, Pentium, Core i3 or Core i5 with integrated graphics and a Core i5 or Core i7 without graphics. However, using a chip with integrated graphics on a P55 motherboard will (in addition to likely requiring a BIOS update) not allow use of the on-board graphics processor, and likewise, using a chip without integrated graphics on a H55, H57 or Q57 motherboard will not allow use of the motherboard's graphics ports.[2]

    http://en.wikipedia.org/wiki/LGA_1156
     
  5. mpe macrumors regular

    Joined:
    Sep 3, 2010
    #5
    It is not good idea. Thermal Design Power of Core i3-550 is 73W while i5-760 is 95W TDP CPU. Most likely the cooling system and PSU, fans are not ready to accept the hotter CPU. You can easily fry it.

    iMac is not typical PC desktop where there is a plenty of air that can eat all the heat and where you can simply put better power source or cooler.

    If you really want to upgrade try i5-660, which TDP is also 73W. This is the CPU Apple offer as optional for 21.5" model. But the performance increase will be modest.
     
  6. product26, Nov 21, 2010
    Last edited: Nov 21, 2010

    product26 macrumors 6502a

    product26

    Joined:
    May 30, 2005
    #6
    I trust that Apple has designed the cooling system to be more than adequate. Think about it... the iMac is not designed to be opened, and cannot easily be cleaned and cleared of dust and buildup. SO the cooling system must be enough to keep up with an average amount of dust inside. I'd guess that you could easily get away with it as long as the PSU can deliver enough power.


     
  7. TMRaven macrumors 68020

    TMRaven

    Joined:
    Nov 5, 2009
    #7
    I'd be more worried about the power restraints than the actual heat production. The cooling in the latest iMacs is very good. Just kicking the fans up a few rpm easily cools the internals. It just so happens the default rpms are very low, so the cooling doesn't seem as great.
     
  8. Bkxmnr macrumors regular

    Bkxmnr

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    Feb 9, 2009
    Location:
    Wichita, KS
    #8
    I think it was an i5-680.
     
  9. MindlessJD macrumors member

    MindlessJD

    Joined:
    Apr 19, 2006
    Location:
    Hampshire, UK
    #9
    This sounds like a great idea for an experiment.

    You could always use one of the utilities to speed the fans up constantly to compensate for the extra heat given off by the quad core.

    Keep us posted if you to try it! :D
     
  10. pt0016 thread starter macrumors regular

    pt0016

    Joined:
    Jul 9, 2010
    #10
    Just letting y'all know that seeing as it is almost summer holidays here in New Zealand, I will likely do the CPU replacement then, when I have money and time :)

    Thanks for all the thoughts, and I don't see how it wouldn't work... :p
     
  11. pt0016 thread starter macrumors regular

    pt0016

    Joined:
    Jul 9, 2010
    #11
    Update: I have finally got around to trying the i5 760 in the 21.5" iMac with the Core i3 550.

    It doesn't work. After 2 hours of gutting my iMac, when I turn it on, there is no video, and after a while, the fans ramp up to full speed. Any ideas on how to get it working? Or I'll be chucking back the old CPU. I read the other thread, similar to this, http://forums.macrumors.com/showthread.php?t=812500 , and they also get no video. Maybe it needs new firmware?? :confused:
     
  12. Bkxmnr macrumors regular

    Bkxmnr

    Joined:
    Feb 9, 2009
    Location:
    Wichita, KS
    #12
    Maybe you should reset the PRAM, NVRAM, SMC, and PMU (and whatever else is resettable).
     

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