In the next year several fourth generation machines with performance in the 100 million instructions per second range will become available. The Illiac IV is one of these machines. With the advent of these machines it will become practical to include an extra dimension, or to greatly increase the resolution of many mesh calculations. Problems which are currently constrained to two spatial dimensions can be expanded to three dimensions, and problems which are currently limited to one spatial dimension can be expanded to include two. This expansion in dimensionality and refinement in resolution implies an increase of approximately two orders of magnitude in the size of the problem's data base. The Unicon 690 mass-memory system will have two distinct uses in the Illiac IV system. The primary use of the Unicon 690 will be to act as a replacement for the conventional restart-output tapes which are generated in the course of large mesh calculations. The Unicon 690 will also act as a storage resource for the Advanced Research Projects Agency (ARPA) network. The ARPA net is a collection of some twenty computers, interconnected by a 50 000 bit/s network of telephone lines and interface message processors. To facilitate the use as a resource on the ARPA net, a conventional computer will be interfaced to the 690 to act as a file manager. Performance parameters of the Unicon 690 are certainly not optimal for this requirement. As is generally the case, higher transfer and lower access time are desirable.