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Implementation of a new instruction set architecture (ISA) is a non-trivial task which involves significant modifications to the system software, such as the compiler, the assembler, and the linker. This task also includes modifying and verifying functional and cycle accurate simulators to facilitate correct simulation and performance evaluation of programs under the new ISA. Isolating errors in these software components becomes extremely challenging and demands automated and semi-automated mechanisms since neither the compilation infrastructure nor the simulation infrastructure can be trusted as both parties have been heavily modified. Bootstrapping a new ISA is very common in embedded systems since there is a greater variety of embedded ISAs due to often not having a need to support backward compatibility of executables. In this paper, we present the tools and the verification mechanisms we have implemented to support the development of a number of related, but distinct ISAs. These ISAs are similar in complexity to the RISC-V ISA, and range from simple pipelined and superscalar processor ISAs, to a complete VLIW ISA. Our work in developing the system software and simulators for these ISAs demonstrate that a step-by-step semi-automated approach which relies on simple invariants can facilitate effective bootstrapping of the complete system software and the simulator infrastructure. 

To sustain the higher education industry and address U.S. economic downturns, researchers must prioritize research on undergraduates aged 24 or above – contemporary students. This empirical study finds contemporary students have lower chances of attaining degrees—any degrees—than their younger peers. Using nationally representative U.S. data from the Beginning Postsecondary Longitudinal Study, our interaction models reveal that the penalty experienced by contemporary-age students is more significant at four-year colleges where older students are less than half as likely to attain degrees as their younger peers. Transferring also distinctly and positively enhances the predicted probability of degree attainment for contemporary-age students (p < .000), reducing the age penalty. Our findings underscore the significance of prioritizing contemporary students in research and practice to increase degree attainment. We close with implications for practice, policy, and research.