The bit was automatically set to indicate whether the word had been rewritten since it had last been written into and could be set to indicate that the memory location had been read. The value of the full-empty bit could be checked in one machine cycle. It had a UNIX environment and was front-ended by a minicomputer. Since it was at the very high end of performance, it exposed the hardcore scientific users to parallelism, although initially mostly in a negative way. In a way, though, the CRAY X-MP multiprocessor legitimized parallel processing, although restricted to very large grain, very small numbers of processors.
Memory is shared among all processors.
These systems were serious attempts to design and demonstrate a shared-memory architecture that was scalable to very large numbers of processors. They featured an interconnection network between processors and memories that would avoid hot spots and congestion. Unfortunately, these systems took a great deal of time to construct and it was the late 1980s before the IBM RP3 existed in a usable fashion. At that time, it had 64 processors but each was so slow that it attracted comparatively little attention. The architecture is certainly still considered to be an interesting one, but far fewer users were exposed to these systems than to other designs that were constructed more quickly and put in places that allowed a large number of users to have at least limited access to the systems for experimentation.