Development of novel technology (Application Emulators/HLAM/PetaSIM) to support rapid prototyping of new computer architectures and new system software. This process will make it possible to provide reasonable estimates of the performance that will result from running realistic applications on future very high end architectures, such as those contemplated in the PetaFlop initiative. In order to support the need for rapid prototyping, the process will be robust and relatively fast.