Undervolting Your Laptop’s CPU

Laptops are only as portable as the battery life they can give you. Most of today’s Pentium-M and Core Solo/Core Duo systems have grown efficient at handling power-related issues, and can usually run upwards of three hours on each charge (the standard is usually four hours). The basic principle behind this is that the Pentium-M based processors have enhanced SpeedStep, which means the computer can adjust the processor’s clock speed to match the processing requirements of the applications being run at any time. AMD’s Turion 64 mobile chips also have their equivalent, and even the lower-end Sempron chips can halve their clock speeds when the demand for processing power is low.

However, those who use other chips, such as the less expensive Celeron-M, do not enjoy the power efficiency features of enhanced SpeedStep (or Power Now! for AMD). Hence, while processing power is at par with their higher-end counterparts, it is the battery life that suffers.

Also, even users who have machines based on the Pentium-M might want to tweak their systmems to squeeze out a further few minutes or hours of battery life. Or the issue might even be related to heat dissipation (which is indicative of inefficiency and loss).

I ran across an article on NordicHardware.com that describes how to undervolt a laptop’s CPU. The theory is that CPUs can actually run at a lower voltage than standard, and underpowering one’s chip can ideally lead to less consumption usually without much adverse effect on performance.

If you perform the undervolting correctly, calmly and if you decrease the CPU voltage step by step I can only say this; you have nothing to lose! … This will lower the amount of heat the CPU emits. This will result in a cooler system. And heat is always a problem when it comes to laptops.

So you get a colder laptop, which is nice if you like to keep it in your lap. The second problem with laptops is the battery time. When you lower the voltage of the CPU, it will not consume as much current! This of course leads to a longer battery time. In the end the difference could be a whole lot and were talking ten (or so) minutes and not a few trifling seconds. Would you say no if you got more time in front of your laptop?

Looking at undervolting in a long-term, a cooler CPU should give the computer a longer lifetime. Of course, we can’t know this in advance but there is always a possibility that the computer lives on a few years longer.

I’m currently trying out throttling my machine’s CPU. I use a Celeron-M, so my computer doesn’t have enhanced speedstep, nor can it support changing the voltage (like with the AMD Turion). However, I’ve installed the RM Clock utility, which enables CPU throttling for real-time or on-demand performance. So far, the utility tells me it’s able to throttle down the CPU frequency to as low as 300MHz, incrementing upward whenever processor load increases. I have yet to see gains in terms of battery performance, though, and I will post on my observations after a few days of real-world testing.

I’m aware some laptop manufacturers have their proprietary power-saving utilities, like Asus’ Power4 Gear utility. Anyone care to share his/her experiences with such utilities that help (or at least try to) maximize battery life?

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