Undervolting Macbook Pro

Discussion in 'MacBook Pro' started by LPA5000, Jul 20, 2008.

  1. LPA5000 macrumors newbie

    Jul 18, 2008
    Tired of nearly burning my thighs with my Macbook Pro, I Googled around to find available notebook cooling methods, and came across something called “undervolting,” a way to lower the amount of heat a CPU emits. This appealed to me over other cooling options because: (1) I wouldn’t have to buy a fanned cooling pad; and (2) although installing smcFanControl seems like a good choice, I don’t think it gets at the heart of the issue—i.e., the cause of the heating (it just speeds up the notebook’s fan).

    It appears that CoolBook is the only undervolting program for Mac OS X, so I purchased it, expecting undervolting to be self-explanatory and easy to set up. I was, of course, wrong. Not being a computer expert, I searched for guides explaining how to undervolt, but most were too technical and jargon-riddled for my understanding.

    I continued to setup CoolBook anyway, and did the best I could, but am still not totally confident in my CoolBook configuration. So, I’m going to explain step by step how I set up CoolBook on my Macbook Pro, and would like an expert to look over it and make sure I didn’t screw up. I’ve underlined sections that I’m particularly curious/confused about.

    Note: I am well aware that CoolBook only partially supports “Santa Rosa” Macbooks (I had to look-up “Santa Rosa”). I’m pretty sure my Macbook Pro is a “Santa Rosa,” as I only purchased it last May; this means it has a Penryn-based processor, right? Anyway, according to the CoolBook manual: “The CPU of the "Santa Rosa" / LED MacBook Pro can be read and controlled using CoolBook, and the maximum power consumption may be reduced. There is however an issue, making this model consume more power running in idle battery mode with CoolBook activated.” This does not really worry me, as I rarely leave my Macbook idle while running only on battery.

    Now, here are the steps I took:

    Download, purchase, and install CoolBook.

    Uncheck “Throttling active.” “CoolBook active” remains checked.

    Now, frequency-voltage pairings must be added to the Adapter. To do this, select each frequency in the frequency drop-down list one by one, in numerical order; for each frequency, also select a corresponding voltage in the voltage drop-down list. The goal is to select the lowest voltage possible for each frequency. Clicking “Set” will activate that frequency-voltage pairing, allowing the user to test whether or not the pairing is safe to use.

    This requires, however, some trial-and-error, because if the frequency-voltage pairing is unsafe, the computer will have an instant kernel panic, and shut down. (At this point, one would turn the notebook back on, reopen CoolBook, and select a higher voltage for the offending frequency.) To determine whether or not a particular pairing is safe, we use CPUTest (that is, if the computer hasn’t already had an instant kernel panic). If the pairing passes CPUTest, click “Add,” and the pairing will appear in either the Adaptor list or the Battery list, depending on which is being altered. Next, click the “Save” button. Allow CoolBook to test the newly saved settings. Do this for each frequency in the drop-down list. (To reduce tediousness, I only ran CPUTest on the smaller frequencies and the larger frequencies. It became clear after a short while that all the lower frequencies would get the same voltage—0.95 V, the lowest one.)

    Note: To be completely honest, I don’t really understand how CPUTest works. All I know is its function for my current purpose: to test whether or not the active frequency-voltage pairing is safe. Here are the CPUTest options I set, some recommended by the CoolBook manual:

    Test type: CoolBook recommends selecting “Huge,” which I did for the smaller frequencies. For 2300 and 2400 MHz, I selected “All,” as it seemed like a more rigorous standard with which to test the frequency-voltage pairing.

    Repetitions: 1 (I can only guess that this option allows CPUTest to run the test multiple times.)

    Instances: I have no idea what this option does, but the CoolBook manual recommends selecting “2,” which I did.

    Now, what exactly is B/2? The CoolBook manual reads: “Check this box to use the frequencies with half bus speed. ‘Santa Rosa’ only.” When I check this item, the frequency drop-down list changes to include 600 MHz to 1200 MHz. As done with the earlier frequencies, I paired these with voltages, and added them to my Adapter list.

    After completing all the aforementioned steps, I ended up with the following list in my Adapter:

    600 Mhz / 0.95 V
    700 Mhz / 0.95 V
    800 Mhz / 0.95 V
    900 Mhz / 0.95 V
    1000 Mhz / 0.95 V
    1100 Mhz / 0.95 V
    1200 MHz / 0.95 V
    1400 MHz / 0.95 V
    1600 MHz / 0.95 V
    1700 MHz / 0.95 V
    1800 MHz / 0.95 V
    1900 MHz / 0.95 V
    2000 MHz / 0.95 V
    2100 MHz / 0.95 V
    2200 MHz / 0.95 V
    2300 MHz / 1 V
    2400 MHz / 1 V

    Throttling level: Very High
    Temp limit: Off

    I repeated these steps for the Battery list (though it went much quicker), and the results came out exactly the same as in the Adapter list. Also, I don’t know if this matters, but it made sense to me to unplug my notebook while configuring the frequency-voltage pairings in the Battery list. I figured that if I’m testing the battery pairings, then the notebook should be running on battery. Was this necessary?

    Lastly, I turned on throttling by checking “Throttling active.”

    Other questions:

    Must I have a frequency-voltage pairing for each and every frequency? In some screenshots I’ve seen, it looks like people have only a couple pairings.

    When setting the frequency-voltage pairings, should I be in Safe Mode? Does being in Safe Mode prevent instant kernel panics?

    In CoolBook Preferences, what exactly is the User/Password for? Is that only for notebooks that have multiple login accounts?

    Well, I hope that all made sense!

    Until I hear from an expert on this, I’ve deactivated CoolBook to avoid any possible damage to my CPU.

    And, finally, here are my system specs, because I guess they’re important:

    Mac OS X 10.5.4
    Processor Name: Intel Core 2 Duo
    Processor Speed: 2.4 GHz
    Number Of Processors: 1
    Total Number Of Cores: 2
    L2 Cache: 3 MB
    Memory: 2 GB
    Bus Speed: 800 MHz

    All help and information is greatly appreciated.
  2. robojenny macrumors newbie

    Jul 25, 2008
    First, there is another thread post here that may help you some: http://forums.macrumors.com/showthread.php?t=460146. I'm no expert, but I will attempt to answer one of your questions.

    No, it is not necessary. Excluding a frequency however, will make it so your laptop will not run at that clock speed. Removing slower speeds will have your computer run faster even if it's getting hot. Removing faster speeds will help conserve energy, particularly useful when you are stuck being on battery power for a long time.

    Undervolting shouldn't damage your CPU. It just may become unstable since you won't be giving it enough juice to run so a core will shutdown. I am using it myself on my Macbook Air (if you're curious about my experience, read here: http://www.robojenny.com/2008/07/undervolting-macbook-air.html)

    Sorry I wasn't able to answer more of your questions. Hopefully the link to the other thread will help you though. Good luck.
  3. XandeR803 macrumors member

    Jul 25, 2008
    I've been in contact with the author about this issue. It's not an issue with CPU because that undervolts perfectly fine. The issue is with the GPU. All the Santa Rosa models use the 8600m chip and it's not detecting idle properly when coolbook is active. As such, when on battery power the gpu is not going into full idle mode so it's consuming more power then it should. I was able to verify this myself when running on battery w/ coolbook active I was only able to get about 3 hours of battery life whereas normally I get about 4:30 (light surfing and e-mail). Last I heard the author was working on an update to correct this issue so until it's fixed I will leave it disabled.

    Also, looking at your speed steps for adapter, I think you have way too many. It's probably not necessary to create a step for every speed as I don't even believe the default setting is to step to every speed. Perhaps when you're on battery you may want more finely tuned speed adjustments for battery life purposes but they don't really serve a purpose when plugged in, especially since you're using the same voltage for most of them. Personally, when plugged in I want the laptop to run as fast as possible so I would just have several speed settings:


    Maybe one or two more in between there depending on the heat generated at those speeds but that should be more than adequate. With fewer speed steps I would also lower the throttling level so it spends more time in each step.
  4. LPA5000 thread starter macrumors newbie

    Jul 18, 2008
    Robojenny and XandeR803, thank you both for your help!

    I've reconfigured CoolBook as follows:

    800 MHz / .95 V
    1200 MHz / .95 V
    1800 MHz / .95 V
    2400 MHz / 1 V

    800 MHz / .95 V
    1200 MHz / .95 V
    1800 MHz / .95 V
    2200 MHz / .95 V

    Throttling: Medium

    Also, in case you were curious what my default settings were:

    800 MHz / .95 V
    1200 MHz / 1 V
    1400 MHz / 1.025 V
    1600 MHz / 1.05 V
    1800 MHz / 1.075 V
    2000 MHz / 1.1 V
    2200 MHz / 1.125 V
    2400 MHz / 1.1375 V

    I think the default throttling level was set to medium.
  5. winninganthem macrumors 6502a


    Jun 10, 2008
    How well is this working for you?

    Any advantage to doing this opposed to just buying a lapdesk to protect your lap?
  6. Demthios macrumors member

    Jul 27, 2008
    Okay I'm a noob with macs but how do I find the preference box so that I can active this program? I can't seem to find it anyway I see inside of the package under resources where the code is but I can't find the actual app to do run it with...any help would be great.
  7. robojenny macrumors newbie

    Jul 25, 2008
    The biggest advantage for me is when running on battery power, the battery will last longer, naturally since you're using less of it to power your laptop. A lap desk won't help that whatsoever. It can also help your fan run less often, which is nice. I hate it when I hear my fan running all the time. Theoretically, you can run at the higher clock speeds more frequently if your laptop is cooler, since the throttling won't pull it back to a lower clock speed as much because you're not getting close to the threshold as often.

    I also have a laptop cooler (like this) that I used to use with my PC (Dell XPS Gen 2). The laptop cooler has two fans built-in and is powered by USB, but I much prefer having the laptop itself run cooler than to have something else try to cool it.
  8. XandeR803 macrumors member

    Jul 25, 2008
    How's your battery life with those settings?
  9. deltaiscain macrumors regular

    Jul 24, 2008
    I just did this on my Penryn MBP, and...well... the figures are insanely low. for the highest clock speed, 2.5GHz, i have 0.965, and for all the other ones 0.9500. Haven't had any kernel panics yet, and i did do the stress test. My temps are now super low, and I'm shocked that my values are so low, and that they were so high on their defaults
  10. MrZebra macrumors regular

    Sep 7, 2008
    Thank you for sharing. Is there anybody who tried this? I'm interested to hear :D
  11. sascha h-k macrumors 6502

    sascha h-k

    Apr 26, 2004
    vienna / austria
    i use coolbook since long time .. (best temp. & fan app around)

    the easiest way of setup is: check throtteling active, default and then run with ac connected "save".

    this will test and setup your ac and battery settings ..

    restart and don't forget to choose "your" temperature ..

    my mbp runs with 55° celsius, about.
  12. deltaiscain macrumors regular

    Jul 24, 2008
    Actually, i just had one kernel panic on those settings. my fix, turn the 2.5GHz up by one, to 0.975. now, it's rock solid, and i've stress tested it, plus played COD4 for an hour, and no problems.

    One other issue I have is that VLC player now lags when watching videos. The fix is to use quicktime player.
  13. bobthebob macrumors newbie

    May 18, 2009
    hey there - i have the 1st gen MBP 17" and over the course of the last year it's begun to run SUPER-HOT, i use SMC Fan Control which helps, and i put some larger rubber/plastic "feet" on the bottom of the MBP for better airflow - but unless i have the fan set to 6000 rpm (maximum) or thereabouts i can't get thru an entire movie. the GPU gets so hot that the display just freezes. i actually took the whole thing apart and reapplied a thin layer of fresh thermal paste on the CPU but it didn't seem to help at all!
    anyway i was totally frustrated and did a google search where i heard about this app - so this is my last hope - i can't afford a new machine right now.
    so a few hours ago i purchased and installed Coolbook and i have a few questions:
    do i need to keep the controller app running? i'm guessing not, but it's not all that clear... of course that seems to be the only way i can monitor the settings so...
    also - i tried using the temp limit drop down menu but i kept on having kernel panics - they went away (using the same settings) once i turned it off. has anyone else had this experience?
    here are my current settings:

    2171 1.15V
    throttling level - Low

    both for adapter and battery

    using these (and with Fan Control set to 2000rpm) i seem to have a 'normal' running temp of around 60-65 deg C. this is with me simply running Safari, Pathfinder, Vuze and the like - nothing even GPU intensive. this seems to be exactly the same as without Coolbook... so perhaps my settings aren't correct? should i add more settings? and is it advisable or even necessary to use the same Voltage for multiple Freqs?

    also - one last thing - i notice (in the menubar display) that the processor Freq jumps from 2171 to around 1002-5 Mhz and then back again... why does it do this?

    i'm grateful that someone went to the effort to create this app - buti have to say that the documentation is pretty awful. i'm a fairly savvy guy Mac-wise (hell i took this entire thing apart put it back together - and it still works!) but i can't really make heads or tails out of the "manual"
    perhaps others could post their settings that work for them?
    i'm really just interested in reducing the running temp.
    thanks in advance,
  14. sascha h-k macrumors 6502

    sascha h-k

    Apr 26, 2004
    vienna / austria
    hi bennett
    you have to pull coolbook (hide) in the startup items to see the actual temp.; check throtteling active and 2nd coolbook active, set temperature to 55°c.

    start save with default, as i wrote above ...

    beside this look in activ-monitor what cpu load you get when nothing is running; should be about 98% idle ..
  15. bobthebob macrumors newbie

    May 18, 2009
    thanks sasha - actually i'm not really sure what you mean by "start save with default" - i thought the point was to *change* the default settings?
    activity monitor shows about 90-95% idle (i have a lot of 3rd party utilities running).
    and as far as setting the temp to 55 - can you (or any one else) first explain exactly what this function does?
    thanks a lot,
  16. deltaiscain macrumors regular

    Jul 24, 2008
    Hmm, i have two different temperatures:confused:
    Coolbook is giving me 35C and SMC fancontrol is giving me 45C

    Any idea which one is the correct one?
  17. sascha h-k macrumors 6502

    sascha h-k

    Apr 26, 2004
    vienna / austria
  18. deltaiscain macrumors regular

    Jul 24, 2008
    It's saying the same as SMC. Too bad, hoped it would be way lower :p
  19. sascha h-k macrumors 6502

    sascha h-k

    Apr 26, 2004
    vienna / austria
    this is the answer from developer:

    Hi Sascha,

    iStat uses different sensors.
    No, you need a new license. (i asked if a transfer to another mbp is possible)


    Magnus Lundholm
  20. Mactagonist macrumors 65816

    Feb 5, 2008
    NYC - Manhattan
    anyone using Coolbook with the Unibody MBP? I used it on both my Macbook Air's and I was very happy with it then.
  21. sascha h-k macrumors 6502

    sascha h-k

    Apr 26, 2004
    vienna / austria
  22. jman995x macrumors regular

    Sep 8, 2007
    My MacBook Pro 17" has been running a little hotter than normal lately and I've been toying with the idea of undervolting it.

    I have some questions though:
    1. What is the normal temp range I should expect my MBP 17 to run at (no undervolting or laptop cooler)? I've been keeping an eye on my "Fan Control" program and the temperature seems to vary between 64*C - 80*C. Is that within the normal range? Also, my left and right fans run pretty constant around 5,000 RPM (at 69*C). Is that normal as well?
    2. I've also been reading everybody's posts about CoolBook and think I'm definitely going to go that route, but need to know if I have to reboot my computer for the changes to take effect. I have a program up and running that I don't want to shut down (and of course I'll have to shut it down if I have to reboot after setting up CoolBook).

    If anybody else has a 2.33GHz Intel Core 2 Duo / 667MHz MBP 17" and has used CoolBook, can you share your experience and let me know what final steps/settings you settled on so that I don't have to go through kernel panics and reboots?

    Those are the only questions I have right now.

  23. Dan73 macrumors 6502a

    Jul 30, 2009
    Coolbook was one of the first thing I bought for my 13" MBP when I got it. Running cooler is ALWAYS good.
  24. jman995x macrumors regular

    Sep 8, 2007
    Did you have reboot your computer after you changed the settings in CoolBook?
  25. reallynotnick macrumors 6502a

    Oct 21, 2005
    I'm pretty sure you need to restart CoolBook the first time you use it to make it active, because every time you turn it on or off you have to restart for the effect to take place. Also I assume you have already paid for it because it won't do anything if you don't.

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