Conclusions

The majority of the hardware and the operating-system software on an AS/400 is dedicated to I/O, and this is not likely to change in the future. The rapidly increasing performance of processors continues to strain most I/O systems. The physical devices simply cannot improve in performance nearly as fast as processors. To keep up with the increasing demands of higher-performance systems, more and more devices and the control of these devices will have to occur in parallel.

The AS/400, with its use of multiple buses and multiple IOPs, is uniquely positioned in the industry to take advantage of the tremendous growth in both system capacity and performance that is anticipated to occur in the next few years. This use of programmable I/O processors and the capability to perform massive numbers of I/O operations will distinguish the AS/400 for many years to come.

It is interesting to note that the first system to use programmable I/O processors was the CDC 6600. CDC called its I/O processors peripheral processors. You may remember that the CDC 6600, designed by Seymour Cray, had the first general-purpose load/store processor to use pipelining. This design led to RISC processors. Perhaps this first supercomputer also knew something about I/O. Today’s AS/400 certainly learned some lessons from it about building high-performance systems.