Virtual Prototyping, a Case Study in Dataflow Oriented Codesign.

The main topic of this paper is a discussion of the design process we haveused during development of an application specific computer system.We will focus on a case study involving a 3D computer graphics systemwe are currently developing, and how such a system can be optimized for speed.The paper focuses on {\em how} a design is developed, in order tosatisfy a set of requirements. In particular, we discuss the importance ofalways having a running software prototype of the entire system available.This software prototype also serves as the main medium forexperimenting with new ideas for the algorithms, and the partitioning ofcomputation blocks, memory and communication channels to either hardwareor software. We call this process {\em Virtual Prototyping}, during whichwe are able to apply transformations to the design, eg. {\em Loop Fusion} and {\em Strip Mining} to improve data locality.An interesting consequence of this is that at the systemintegration scale the optimizations we perform to acheive good hardwareperformance, are in fact also contributing to improving the executionspeed of the software prototype.