The Usefulness Equation

Software to Keep Your MacBook Cool

- 2008.11.25 - Tip Jar

Sometimes our Apple notebooks can really burn up. Some tips on how to keep the temperature down.

With great notebooks, comes great heat!

Maybe that's not how the quote went, but it certainly holds true. Heat is, in essence, our greatest enemy when it comes to electronics. Nothing will strain the system more. (Sand, dirt, dust, liquids...)

A couple interesting things to note about the MacBook (and most, if not all, Apple notebooks) is that the processors are Ball-Grid Array. That means instead of a socket into which the pins of the processor fit, these processors have tiny pads into which minuscule balls of solder are melted and then bonded onto the motherboard. (Or vice-versa, depending on the manufacturing process.)

There are some obvious advantages to BGA. It shaves off the millimeter or so required for the socket. It's cheaper to manufacture. It also discourages customers from processor swaps, which keeps the lines firm between price points.

However, I've always kept a watchful eye on my high temperature BGA chips. Heat cycles will deteriorate the strength of the solder, the motherboard itself, and even the package (processor). It is most apparent around the processor, GPU, northbridge chip, and battery charging circuitry. Like any material in a compromised state, it will eventually break.

Here are the factors that affect your processor's temperature the most.

  1. Processor Clock Frequency - The higher the clock frequency of the processor at the current moment, the higher its heat output will be. There are complex math equations to figure out the TDP - the amount of heat that will be needed to be dissipated by the cooling system based upon clock frequency and voltage.
  2. Processor Voltage - Just like clock frequency, the higher the voltage of the processor, the more heat it will produce. Voltage is supporting the processor though, so taking away too much will lead to errors.
  3. Processor Load - The processor will inherently get warmer when it is working harder. (It's too bad it can't sweat to help cool itself down.)
  4. Fan Speed - The more air the system is moving over the heatsink(s), the cooler the processor will be. This is because the air picks up the heat that the heatsinks are removing from the processor.
  5. Throttling - The processor has the ability to change it's Clock Frequency and Voltage within a certain set of values to run cooler. This is called throttling.

The goal of this article is not to instill mass paranoia around Apple's motherboards - I have many Apple BGA machines that are pushing limits in terms of longevity. The goal is to show some effective ways at making the heat cycle much more shallow and removing some strain on your components.

We'll examine some awesome software to help you out.

In terms of software, there is the mother of all (Intel-based) fan control. smcFanControl 2 (free, donations accepted) has various improvements over version one. The Apple fan driver sparingly activates the fans until it reaches a high temperature threshold. With this utility, you can bring that threshold down to what you want it to be. I set my on-battery speed to 3000 RPM and my AC adapter (charged) at 5000 RPM. The only time the fan will run at maximum speed (~6200 RPM) is hen my MacBook is charging.

For people who are concerned about noise, the fan becomes noticeable at roughly 5000 RPM. Keep it at 4500-4800, and you should have a good medium between noise and cooling. For those concerned about loosing battery life because of the fan running faster, use this trick in conjunction with my next one.

Secondly, we have CoolBook. For those unfamiliar with it, CoolBook allows you to downclock and undervolt your processor. While those may sound intimidating, this app makes it an easy task. When I'm on my power adapter, my processor frequency does not come above 1.33 GHz and the voltage is at maximum 1.0V. My battery values are 1.0 GHz and minimum processor voltage (0.95 V).

In CoolBook, there is a list of values. Click the Adapter button in the top left corner. The list now displays your processor throttling steps. Moving the steps from 1837 down to 1336 and changing the voltage for 1336 to 1.0 V is how I achieved my setup. I attempted to go lower than 1.0 V, but my processor would not go that low at that frequency. It's all trial and error.

I should point out that there is no amount of undervolting that can damage your processor. Still, during the testing process avoid having important data open. There is a possibility of a kernel panic if the voltage is set too low.

My first generation MacBook 1.83 GHz temperatures are:

  • At idle - 38-40°C
  • 50% CPU load - 45-47°C
  • 100% CPU load - 50-55°C

I've never seen it spike above 57°C, which is below my initial goal of 60°C. The average temperatures on these machines are sometimes close to 75°C at 100% load. These techniques will add some longevity to my machine and ensure that it stays well below egg-frying range.

I should add that CoolBook costs 10$. A worthy purchase, in my humble opinion.

For people who use their machines for time-based processing (video editing, photoshopping, etc.), the CoolBook mod will increase time for those tasks. It is effectively chopping off the top end of your processor's throttling. If this is a problem for you, just stick to smcFanControl.

Please note important things about these programs. smcFanControl does not hold your fan speed at the set level, so if your processor temperature spikes, OS X will still be able to increase the speed past the level you set to keep your machine from overheating. Additionally, CoolBook does not permanently change your throtting procedures. Simply revert to defaults and your original settings are restored.

A couple general usage guidelines:

  • Keep your notebook off your bed, pillows, and out of any cloth or insulating material.
  • Get a cool pad for your notebook on your desk. There are a variety of them out there; get the one that appeals most to you.
  • Remember to crank up the fan speed if you're going to be doing lots of processor intensive activity.
  • If possible, keep your notebook out of excessively dusty areas.

Overall, these tricks will help improve the longevity of your machine. They will also extend the life of new thermal paste/pads by not exposing them to especially high temperatures.

Next time we'll tackle the regular cooling system maintenance you should be performing. LEM

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