OS X 10.5.3 (and beyond) Increases CPU Power Draw?

Discussion in 'Mac Pro' started by jsurpless, Sep 3, 2009.

  1. jsurpless macrumors member

    Joined:
    Aug 6, 2009
    #1
    Hi all

    I've got another ongoing thread (2006 Mac Pro Elevated CPU Temps) where I've been attempting to determine why my 2006 Mac Pro was running so much warmer than I recall at time of purchase...

    By sheer luck, I seem to have stumbled on the cause... when I first noticed it, I was running 10.5.7 with the CPUs idling around 130F or so... as noted in that thread, I tried all sorts of things such as cleaning the dust out, reapplying the thermal paste, etc... all of which had no impact... for an unrelated issue, I decided to re-install OS X 10.5 base version and I was shocked to discover my CPU temps back down in the mid-90s F or so...

    I happened to have taken some screenshots of Hardware Monitor and was able to compare them against the current readings... under OS X 10.5 -> 10.5.2, each CPU draws ~10W @ idle; under 10.5.3 and beyond, the CPU draw increases to ~30W @ idle. Naturally, this extreme increase results in the aforementioned temperature increase... I'm not sure as to the cause but my immediate suspicion is that some low-power CPU mode is disabled in the later revisions...

    I've spoken to Apple about this and they're looking into it but in the mean time, I was wondering if anyone has any input on this?

    -Justin
     
  2. Infrared macrumors 68000

    Infrared

    Joined:
    Mar 28, 2007
    #2
    Is that something to do with SpeedStep?
     
  3. jsurpless thread starter macrumors member

    Joined:
    Aug 6, 2009
    #3
    I'm not sure what is meant by "SpeedStep"?
     
  4. gugucom macrumors 68020

    gugucom

    Joined:
    May 21, 2009
    Location:
    Munich, Germany
    #4
    Speedstep is a technology where the CPU steps down the internal voltage and frequency when it senses idle.

    http://en.wikipedia.org/wiki/SpeedStep

     
  5. jsurpless thread starter macrumors member

    Joined:
    Aug 6, 2009
    #5
    So maybe this has been broken in some capacity in 10.5.3 and after?

    My CPU voltages are ~1.3 and ~1.15 in 10.5.3 and 10.5.0, respectively...
     
  6. jsurpless thread starter macrumors member

    Joined:
    Aug 6, 2009
    #6
    Are others observing similar behavior? What are people seeing for power draw at idle?
     

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