Whither configurable computing?

Configurable computing has captured the imagination of many architects who want performance of application specific hardware combined with the flexibility of general purpose computers. Despite the efforts of many research groups over the past decade, successes have been rare: configurable computers so far exhibit poor cost performance for most common applications. To make things worse, configurable computers are notoriously hard to program. Commercial FPGAs are not well suited to most applications. These FPGAs are necessarily very fine grained so they can be used to implement arbitrary circuits, but the overhead of this generality exacts a very high price in density and performance. Compared to general purpose processors (including DSPs), which use very optimized function units that operate in bit parallel fashion on long data words, FPGAs are very inefficient for performing ordinary arithmetic and logical operations. FPGA based computing has the advantage only when it comes to complex bit oriented computations like count ones, find first one or complicated masking and filtering. In summary, future progress in configurable computers will result not from continued research along the same FPGA based path, but from a diversity of approaches including more coarse grained configurable architectures and constrained programming models that allow more powerful compilation techniques