Diagnosing hardware problems in core memory required time-consuming diagnostic programs to be run. While a quick test checked if every bit could contain a one and a zero, these diagnostics tested the core memory with worst-case patterns and had to run for several hours. As most computers had just a single core memory board, these diagnostics also moved themselves around in memory, making it possible to test every bit. An advanced test was called a "Schmoo test" in which the half-select currents were modified along with the time at which the sense line was tested ("strobed"). The data plot of this test seemed to resemble a cartoon character called "Schmoo," and the name stuck. In many occasions, errors could be resolved by gently tapping the printed circuit board with the core array on a table. This slightly changed the positions of the cores along the wires running through them, and could fix the problem. The procedure was seldom needed, as core memory proved to be very reliable compared to other computer components of the day.