Three separate versions of the SDI simulations were constructed: Sim87, Sim88, and Sim89. Each was more elaborate and used more capable hardware than its predecessor. Sim87, for example, executed on a single 32-node Mark III; Sim89, in contrast, was implemented to run on the 128-node Mark IIIJfp. Configuration was flexible; Figure 18.10 shows a typical example using two hypercubes and a network of Ethernet-connected workstations. The internal structure of the simulation showed similar evolution. Sim87 was not much more elaborate than indicated in Figure 18.9 but it evolved to the much more capable version shown in Figure 18.11 for Sim89 [Meier:90a], [Yeung:90a].
Figure 18.10: Typical Sim89 Hardware Configuration
Features of Sim89 included more elaborate individual modules, outlined below.
Figure 18.12: A complex strategic defense situation graphically summarized.
The Command Center was an important conceptual step. It re-positioned the role of the workstations from one of passive display of the activities occurring internally to the hypercube, to the role of the key user interface into a network computing environment assisted by large-scale parallel machines. It, in effect, helped us merge our own mental picture of the paradigm of network computing with that of parallel processing and into the more unifying view of cooperative, high-performance computing.