This section will deal with the case where a four-bit field, associated with each 32-bit word in memory, is not used to indicate the type of its contents, but is instead used to indicate such things as whether the word is initialized, or to indicate indirection.
The inspiration for this mode of operation is a computer known as the Tera, which used these additional bits to facilitate the sharing of memory between processors. In this computer, processors and memory banks occupied different locations in a three-dimensional grid, thus giving two processors access to any given memory bank, the ones which shared its row and column. (Columns switched from horizontal to vertical in alternate planes, connected by rows, thus allowing a three-dimensional structure without requiring three ports to each node.)