Which IBM Thinkpads had 64 bit CPUs?

[cogitordi]

Did any of the IBM Thinkpads (not Lenovo) have a 64 bit CPU? And if so, were any of these notebooks able to use 4GB RAM?

[yak]

The answer would be no. Lenovo took over in 2005, first T60 models (T60 was the first 64bit capable ThinkPad) appeared in 2006, initially in 32bit only versions. T60 is limited to 3GB RAM. T61 was the first that could take more. It was released in 2007.