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Computer systems research is a knowledge-based pursuit, but lacks even a rudimentary codification or taxonomy of that knowl- edge. It is unsurprising that the computer architecture literature is difficult to use in designing new systems, especially those intended for production or experimentation. This thesis proposes that the common thread through the literature is the assignment of system functionality to system level (and choice of implementation technol- ogy within that level).
Proper mapping of function to level is critical to achieving accept- able system performance, but there is no methodology with which to make these decisions. This thesis contributes data on the efficacy of functional migrations in a restricted domain, object-oriented systems, using a real computer system as a case study.
This thesis studies an extreme case of traditional functional migration in a commercial product, the Intel 432 microprocessor, analyzes the various architectural and implementation tradeoffs and anomalies, and shows their individual effects on overall performance. The thesis demonstrates that, over a set of six benchmarks, perform- ance can be improved by factors of two or more when these artifacts are removed. Had the technology been incrementally improved, another factor of two or three would have been attainable. Even with this improved performance, the 432 would be from one to four times slower than current conventional microprocessors, depending on the task; this ratio is the object-oriented overhead built into the architecture.
The 432 provides evidence for some key RISC assertions: the value of local data registers, easily decoded instruction formats, and the high cost of procedure calls. Others, such as the performance cost of a complex addressing mechanism, are arguable. The various contributions of architectural features to overall performance are explicitly discussed, so that these results are applicable to other systems, whether object-oriented or not. Downward functional migration is argued to be indispensable for access checking and
expensive common operations, but improper migrations can be detrimental. (Abstract shortened with permission of author.)
*This research has been supported by the U.S. Army Center for Tactical Computer Systems under contract number DAAB 07-82- C-J164. The views and conclusions contained in this document are those of the author and should not be interpreted as representing the offical policies, either expressed or implied, of the U.S. Army or the U.S. Government.