Wednesday, October 20, 2010

Undervolting the Celeron SU2300

One thing I found out about the CPU (Celeron SU2300) in my UL20A laptop is that it doesn’t change the clock frequency nor change the Vcore when the CPU is in an idle state. The CPU is supposed to have some sort of EIST, but apparently other people are also having the same problem with this CPU.

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The default Vcore of the CPU is 1.000V and default clock frequency is 1.2GHz (although I overclocked it to 1.26GHz – BIOS allows to overclock up to 5%). There is no BIOS option regarding the EIST feature either. The CPU is always at 1.26GHz/1V.

So I downloaded Crystal CPUID and went into Function->Intel Enhanced Speedstep Control and set the voltage to 0.9V and it worked. CPU-Z showed the Vcore as 0.9V. That is the lowest I could set. This setting can be invoked from a desktop shortcut. When you double click the shortcut, it would set the Vcore to 0.9V. So I added it to startup. Now, when the laptop boots into Windows, it would set CPU Vcore at 0.9V.

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People are saying it would lower the CPU temps by about 5C, but hardly any battery life improvement. I guess it is still the screen that is eating up most of the juice. Can’t do anything about it, can we? At least this is something.

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