1. An operating method of a storage device which includes a nonvolatile memory and a memory controller configured to control the nonvolatile memory, the operating method comprising: tracking a clock signal; entering a vendor mode of the storage device when the clock signal corresponds to a vendor pattern; and maintaining a normal mode of the storage device when the clock signal does not correspond to the vendor pattern, wherein, in the normal mode, a command received from an external host device is executed according to a first rule, and wherein, in the vendor mode, the command received from the external host device is executed according to a second rule different from the first rule, wherein the vendor pattern includes a pattern in which a waveform of the clock signal includes a plurality of different frequencies.