klietz@uxe.cso.uiuc.edu (06/21/89)
In 1985, I did a study of character-at-time I/O on a Cray-2. Although the quantitative results of those studies are private, I can you some generalizations. In general, it should be noted that the overhead for character-at-a-time processing tends to be proportional to the # of users who are doing it. People don't type faster as computers get faster, thus the overhead in terms of the number of machine cycles consumed per unit of time is a constant. In the meantime, the number of cycles per unit of time that a supercomputer can deliver has increased exponentially with each new model. Thus, the fraction of supercomputer processing power dedicated to keystroke processing is reduced exponentially. For example (these numbers are fake) if we assume that the overhead of 32 people typing in the vi editor was, say, 12% of a Cray-1S in 1985, it would be less than 1% today with a Cray YMP. I concluded that overhead of character-at-a-time I/O is outweighed by the benefit of better user interaction. Cray Research blessed this concept with the introduction of X Windows under UNICOS in 1987. -- Alan E. Klietz University of Illinois at Urbana-Champaign National Center for Supercomputing Applications 152 Computing Applications Building 605 E. Springfield Avenue Champaign, IL 61820 Ph: +1 217 244 8024 ARPA: aklietz@ncsa.uiuc.edu