Flexibility of FPGA Routing Architectures

Chapter 5 discussed the important issues associated with designing good CAD tools for routing in FPGAs. This chapter focuses on a related issue, that of designing FPGA routing architectures. The reader will recall that the results of some routing architecture experiments were already presented, in Chapter 4. Those results concerned the segmentation of routing channels in row-based FPGAs and showed that it is important to tune the segmentation of the channels for the type of K-segment routing that is desired (see Section 5.3.5). In this chapter, more detailed results are presented from another study of routing architectures, this one concerning symmetrical FPGAs [Rose90b] [Rose91]. The approach taken is an experimental one, in which circuits are implemented by CAD tools in symmetrical FPGAs, over a range of different routing architectures. The main CAD tool used for the experimental results is the CGE detailed router that was described in Section 5.4.3.