The University of Illinois says Seattle-based company Cray Inc. will replace IBM as the builder of the Blue Waters supercomputer.
The university says Cray plans to complete the $300 million project next year.
IBM dropped out of the project in August citing cost and technical concerns.
That left the university and the project's primary financier, the National Science Foundation, in a lurch.
When announced in 2007 Blue Waters was to have been the world's fastest computer. A Japanese supercomputer now holds that title.
Blue Waters will run at sustained speeds of a thousand trillion operations a second, a measure known as a petaflop. Planners say that will make it possible to do massive projects such as research on how tornados form.