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How can I underclock the CPU in Windows 7 on a MacBook Pro?
May 21, 2011 3:47 AM   Subscribe

How can I underclock the CPU in my Macbook Pro (2010) in Windows 7?

I've seen a lot of howtos for underclocking in OSX, but what I want to do is simply run a programme that allows me to clock it down by a few hundred megahertz in order to prevent it getting so damn hot when I play Civilization 5. I don't mind waiting a little longer between turns for a quieter and cooler experience.

I've seen RMClock, but it has issues with unsigned drivers in Windows 7.
posted by dougrayrankin to Computers & Internet (7 answers total)
 
May not help but you could try disabling a core to reduce heat.
Check out http://hints.macworld.com/article.php?story=20071028005353629.
posted by PickeringPete at 6:21 AM on May 21, 2011


The heat might be coming from the video chip and not the CPU (which is another way of saying that this might not work).
posted by It's Never Lurgi at 7:54 AM on May 21, 2011


I'm not sure that lowering the clock speed will do what you think. As a first order approximation, every time a transistor switches state, it emits a certain amount of heat (for mosfets, measured in picojoules if not even less). So the total heat energy (in joules) released will be the same for the same task, whether it happens rapidly or somewhat more slowly.

Reducing the clock speed will make the process take longer, but the same amount of heat energy (approximately) will be released anyway. The only way that would make a difference is if the app is pegging all the CPUs, and Civ 5 better not be doing that. If it isn't, then lowering the clock speed shouldn't make any substantial difference.

Think of it this way: the heat release is pulse-code modulated. You're trying to reduce the height of the pulse-code, but the effect will be to instead broaden the pulses. The total area of the pulses will remain the same. The instantaneous power used will be lower, but the long term average power will not change.
posted by Chocolate Pickle at 11:53 AM on May 21, 2011


...unless you severely cranked back the CPU speed, say to 20% of normal or even lower...
posted by Chocolate Pickle at 11:54 AM on May 21, 2011


I'm not sure that lowering the clock speed will do what you think. As a first order approximation, every time a transistor switches state, it emits a certain amount of heat (for mosfets, measured in picojoules if not even less). So the total heat energy (in joules) released will be the same for the same task, whether it happens rapidly or somewhat more slowly.
Though heat/unit time would be lower, hence I would have a cooler MacBook, no?
posted by dougrayrankin at 12:57 PM on May 21, 2011


2nd'ing It's Never Lurgi in that it's likely your video card that's causing all the heat. On my 17" Core 2 Duo MacBook Pro, if I have it set to use the faster/better graphics through the energy saver preference pane (thus enabling the better graphics card), my laptop runs really hot all the time, and extremely hot using any kind of video game.

Try changing your graphics setting on the energy saver prefs to "Better battery life", which will change to the lower powered graphics card - even whilst plugged in (also requires logging out).
posted by qwip at 1:15 PM on May 21, 2011


Though heat/unit time would be lower, hence I would have a cooler MacBook, no?

Only if you really drastically reduced it, so that performance became awful.

The point is that if you only reduced it somewhat, so that the CPU went from 20% average use to 30% or 40%, you wouldn't reduce the heat/time ratio at all. Only if you lowered the clock rate so far that the CPU saturated at 100% and then you reduced it even further would it start to make a difference.
posted by Chocolate Pickle at 7:56 PM on May 21, 2011


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