This page gives an overview of the ThinkPad R400.
Did switchable Graphics models exist? I cannot find any such hybrid model Machine Types, even though there was talk of it in the press and some Lenovo datasheets seem to suggest they did exist
- 2782, 2783, 2784, 2786, 2787, 2788, 2789 AMD Mobility Radeon HD3470
- 7438, 7439, 7440, 7443, 7445, 7446, 7447 Intel Graphics GMA 4500MHD
It appears that some models (such as 2784-R1U) were also shipped with nVidia Ge Force 9300M graphics