1. A semiconductor circuit formed at least partly on a semiconductor substrate and comprising: a plurality of circuit blocks fabricated on the substrate, each circuit block having substantially the same size and arranged in a grid which extends along first and second directions, each block comprising a plurality of circuit modules; at least one redundant circuit module in one of the circuit blocks: and interconnect circuitry including signal lines formed on the substrate alongside the circuit blocks for interconnecting each of the circuit blocks, the interconnect circuitry extending to each circuit block and having at least one programmable connection connecting inside each circuit block, wherein the interconnect circuitry comprises a plurality of interconnect segments along at least one of the first and second directions defined by the grid, each segment including signal lines and redundant signal lines, wherein each segment is connected to an in-line probe pad, whereby testing of segments for defects within and between segments can be carried out by probing of the probe pad.