The rapid progress of manufacturing nanoscale devices is pushing researchers toexplore appropriate nanoscale computing architectures for high density beyond the physical limitations of conventional lithography. However, manufacturing and layout constraints, as well as high defect/fault rates expected in nanoscale fabrics, could make most device density lost whenintegrated into computing systems. Therefore, a nanoscale architecture that can deal with those constraints and tolerate defects/faults at expected rates, while still retaining the density advantage, is highly desirable. In this paper, we describe a novel nanoscale architecture based on semiconductor nanowires: NASICs (Nanoscale Application Specific ICs). NASIC is a tile-based fabric built on 2-D nanowire grids and NW FETs. WISP-0 (Wire Streaming Processor) is a processor design built on NASIC fabric where NASIC design principles and optimizations are applied. Built-in fault tolerance techniques are applied on NASICs designs to tolerate defects/faults on-the-fly. Evaluations show that compared with the equivalent CMOS design with 18nm process (the most advanced technology expected in2018), WISP-0 with combined built-in redundancy could be still 2~3X denser. Its yield would be 98% if the defect rate of transistors is 5%, and 77% for 10% defective transistors.