A semiconductor wafer is fabricated. The wafer has a plurality of dies. The plurality of dies include at least operable dies of a first type and operable dies of a second type different from the first type. The dies of the second type are rendered inoperable, while keeping the dies of the first type operable. The wafer is provided with the operable dies of the first type and the inoperable dies of the second type on it, for testing of the dies of the first type.