The effect of sparse switch patterns on the area efficiency of multi-bit routing resources in field-programmable gate arrays

The increased use of multi-bit processing elements such as digital signal processors, multipliers, multi-bit addressable memory cells, and CPU cores has presented new opportunities for Field-Programmable Gate Array (FPGA) architects to utilize the regularity of multi-bit signals to increase the area efficiency of FPGAs. In particular, configuration memory sharing has been traditionally used to exploit multi-bit regularity for area. We observe that the process of creating configuration memory sharing routing resources often leads to the use of much sparser switch patterns for connecting multi-bit elements to their routing tracks. In this work, we empirically evaluate the effect of these sparse switch patterns on the area efficiency of FPGAs. It is shown that the sparse switch patterns alone contribute significantly to the area reduction observed in configuration memory sharing FPGAs. In particular, our experiments show that, without configuration memory sharing, sparse switch patterns can reduce the implementation area of multi-bit routing resources by 10.4% while configuration memory sharing contributes to an additional 1.2% in area savings. The observation holds over a wide range of connection block flexibility values and demonstrates that efficient switch pattern designs can be effectively used to increase the area efficiency of FPGA routing resources.