A sub-VT FPGA uses a low swing, dual-VDD interconnect scheme to reduce FPGA area per LUT, delay at a constant energy, and energy at a constant delay relative to a conventional design at low voltage. These improvements are made possible by a custom asynchronous sense amp, a separated voltage for memory cells, and an improved passgate interconnect to optimize routing delay with low energy overhead. This sub-threshold FPGA design enables energy efficient and cost effective configurable logic for a wide variety of ULP applications.