*Result*: Tera Taxonomy.

*The taxonomy of the tera candidates includes only shared-memory multiprocessors and various multicomputers (MIMD). A superscalar or extra long RISC, a vector processor, and a processor with thousands of processing elements are just SIMD processors, since they all have a single instruction stream. Two attributes structure the taxonomy: multiprocessors vs. multicomputers; and scalability using a physically distributed vs. a central memory. Scalability measures whether it is practical to construct ultracomputers. The hardware distinction between multiprocessors and multicomputers is whether the system has and maintains a single address space and a single coherent memory and whether explicit messages are required to access memory on other computing nodes. Multiprocessors have a single address space supported by hardware whereas each computer of a multicomputer has its own address space. A multiprocessor has a common work queue that any processor may access and be applied to. But in a multicomputer, work is distributed among the computers or clusters change, work may have to be moved. Several differences between multicomputers and multiprocessors are explained in the article.*