Free vs. Buy-In
The HPC resources at UArizona are differentiated from many other universities in that there is central funding for a significant portion of the available resources. Each PI receives a standard monthly allocation of hours at no charge. There is no charge to the allocation for windfall usage and that has proven to be very valuable for researchers with substantial compute requirements.
Research groups can 'Buy-In' (adding additional compute nodes) to the base HPC systems as funding becomes available. Buy-In research groups will have highest priority on the resources they add to the system. If the expansion resources are not fully utilized by the Buy-In group they will be made available to all users as windfall.