There have been several incarnations of our GPU code for molecular dynamics. The earliest version resulted from our collaborators Professor Pat Hanrahan (Computer Science Department at Stanford) and Prof. Eric Darve (Mechanical Engineering Department at Stanford) and their groups; this version was never released on Folding@home. The next version was written and optimized by V. Vishal and released as GPU1 on Folding@home. Our second generation GPU code (GPU2) on Folding@home was written by V. Vishal, Mark Friedrichs (general code and ATI), Scott LeGrand (NVIDIA port), and Mike Houston (ATI optimizations). They then continued our methods to release our latest iteration, GPU3.