CPU temp really high (70s) but CPU heatsink is 55?

Discussion in 'iMac' started by frega, Aug 8, 2011.

  1. frega, Aug 8, 2011
    Last edited: Aug 8, 2011

    frega macrumors member

    Jul 28, 2010
    This is when gaming, is it unusual? Cos it's usually the other way round.

    iMac (2011)

    Edit: This is with fans turn up quite high (not maxed).
  2. 88 King macrumors 6502

    88 King

    Jun 18, 2011
    London, UK
    Looks right to me.

    The heatsink is cooling the CPU by conduct heat away to the surrounding air. If the temperature of the heatrsink is higher the CPU, then heat will not be able to transfer from the CPU to the heatsink.
  3. dwarnecke11 macrumors 6502

    Nov 29, 2009
    As a point of reference, here are my temps after about an hour of encoding a 1080p movie. Finally putting my 12 GB of RAM to use! I don't have readout for both CPU and CPU heatsink, though.

    Attached Files:

  4. Spike88, Aug 13, 2011
    Last edited: Aug 14, 2011

    Spike88 macrumors 6502a

    Jan 25, 2010
    The iMac "all-in-one" boxes run hot. If you do a google search using "Imac hot" string, you'll see many other folks complaining their iMac runs hot as well. As seen in google search, there is a "negative pattern" - yet many individual folks don't see it. Apple may not admit it but in realty, their 2010 / 2011 iMac insides do run hot. The negative patterns of "too hot" threads on this forum and google search are as clear as day...

    Talking about computer internal Hard Drive temps. Normal operating range for HDs is 35C to 50C. Over 50C and its starting too cook. Higher then 55C and the HD is starting to cook even more. Consistantly above 60C and its major melt down risk.

    With above in mind, one has a few choices... They are:

    A - Run the Factory configuraiton "as is" until it shuts down - from "over the top" boiling. Also accept the risk that long the insides are being cooked, the higher risk of of system hangs, hardware failures and other problems. Drive until it boils over - like some folks drive their vehicle.

    B - Knowing that one's iMac "runs hot" (like some vehicle transmissions - like GM's 4t65E FWD transmission design), one can install their own "proactive" cooling solutions. Simple low cost solutions like removing its under screen memory cover (to allow more air intake). Or, install 3rd party Fan Control Program - like SMCFan Control 2.3. re: http://www.macupdate.com/app/mac/23049/smcfancontrol and inscreasing its fans by 300 RPMs (which is very little increase). These FREE items will make the insides of your iMac cooler. Cooler = lower risk of system hangs, lower risk future h/w failure (from NO longer being over cooked) and overall, increase of longer life. All from increasing Apple's default fan speeds by a small 200-300 RPMs (above their base).

    If wondering, I have a GM vehicle with 4t65E transmission (that "runs hot" by default) and I installed my own aux ATF cooler - even though I do NOT tow anything with this vehicle. It now runs much cooler. And, I installed SMC Fan Control 2.3 in my "always runs hot" iMac tool as well. It now runs much cooler as well. As per factory specs, "extra cooling" isn't needed in either. After all... They want your system to break down AFTER warranty (so you buy replacement parts or a new replacement). In reality, its a good "proactive" idea to install one's own cooling add-ons. Especially since SMCFan Control and removing the memory cover (that cannot be seen anyway) are free "make better then factory" cooling improvements. Especially if the ideas are free cost.

    Long mumblings short... Applying free cost extra cooling improvements works great on my iMac.

    The choice is yours...

  5. drambuie macrumors 6502a

    Feb 16, 2010
    The CPU diode temp is measured internally directly on the silicon, so it would be expected to be a few degrees higher than the heatsink where a heatpipe is conducting the heat away. However, a difference of 20C or more between the CPU diode and heatsink can be indicative of poor heat conduction between the surfaces of the CPU and heatsink. This could be caused by improper thermal paste application.

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