"By enabling rational programming of mammalian cell behavior, synthetic biology is driving innovation across biomedical applications. Using Cas9-variants as core as protein-based central processing units (CPUs) that control gene expression in response to single-guide RNAs as genetic software, we have programmed scalable Boolean logic computations such as the half adder in single human cells. Combining orthogonal Cas9-variants enabled the design of multicore genetic CPUs that provide parallel arithmetic computations. The Cas9-based multicore CPU design may provide opportunities in single-cell mammalian biocomputing to provide biomedical applications."