Running a Driver Test is only applicable when using Mach3 with the parallel port driver. A Driver Test is performed by running DriverTest.exe (C:/Mach3) and it is used to evaluate the quality of the pulse stream being produced by the driver. The graph is a type of timing analyzer which displays a visual representation of the pulse stream currently being produced. Any variations in the graph are changes in timing from one interrupt cycle to another. On most systems, the reported Max Variation should be 15 or less. Even if there are greater variations, it is possible they are below the threshold necessary to create timing jitters, so movement tests should be performed with the machine tool connected to determine if jogging and G0/G1 moves are smooth.