contacts 1903 for connecting to stimulus grid lines 1904 and 6 tester probe contacts 1902 for connecting to encoded response grid lines 1905 tester 401 probes grid line contacts 1903 1902 using a simplified external probe mechanism to input stimulus to the commonly connected die input pads and to input encoded response to the commonly connected die output pads testing occurs on the die as previously described the difference between the test systems of fig1 and fig1 is that in fig1 most of the common pad connections are provided on the wafer 1901 whereas in fig1 most of the common pad connections are provided by the external probe mechanism 1401 the fuses 1906 are included between grid lines 1905 and common pad connections 1907 1910 to provide for the case where a faulty die output cannot be disabled by the test enable signal 609 for example if the tester 401 sets the test enable signal 609 high to enable testing using the present invention and the output pad of die 3 remains enabled outputting a logic level the fuse 1906 between gird line 1905 and the enabled output pad of die 3 will blow whenever the tester inputs an oppose logic level on grid line 1905 without the fuse.