WinDbg, NTSD, CDB, and KD use the same debugging mechanism, so they use the same commands. The only difference between them is that WinDbg has a GUI interface, NTSD, CDB and KD have console interfaces, NTSD and CDB only support user mode, KD only supports kernel mode, and WinDbg supports both.
Note that the NTSD command installed in the System32 directory on older versions of Windows is likely to be a much older version of the debugger than any version of WinDbg that you might have installed on the machine. In this case, the old and new debuggers will have a difference in the commands that they support.
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