Installed a T9900 in my T500.

[Qing Dao]

I bought a T9900 for $50. It is a real production processor, not ES, but it is the BGA version where they added pins to it. If they didn't say that, you wouldn't be able to tell the difference. I previously had a T9400 installed. The T9400 is a C0 stepping processor that runs at 2.53Ghz with a 1066Mhz FSB. The T9900 is an E0 stepping processor that runs at 3.06Ghz with a 1066Mhz FSB. Guess what? C0 stepping Penryn processors are crap. With the T9400 I had premium thermal paste installed but with the T9900 I just used some generic stuff to test it out, so that already puts the temperatures in favor of the T9400 by at least 2*C. Running the processors at full blast with default voltages and the discreet ATI graphics enabled, there is NO DIFFERENCE in temperature. If anything the T9900 runs slightly cooler because it is with generic thermal paste and some of the other reported temperatures in the laptop are 1-2*C cooler. This is all after taking 4 hourly measurements with each setup. I am really happy with the new processor.

The T9400 C0 could barely undervolt (1-2 stepping below default), while the T9600 E0 stepping in my girlfriend's T400 was able to undervolt a lot. Later when I have time I will try undervolting this processor.

[Qing Dao]

Undervolting results are in. The default voltage of the T9900 is 1.1875 and it is stably undervolted to 1.0750. That is a reduction in full-load power consumption of 19%.