The mdb(1) man page describes the features of the new debugger, including its adb(1) compatibility mode. Even in this compatibility mode, differences between adb(1) and mdb(1) exist. These differences include the following:
The text output format of some subcommands is different in mdb(1). Macro files are formatted by using the same rules, but scripts that depend on the output of other subcommands might need to be modified.
The watchpoint-length specifier syntax in mdb(1) is different from the syntax that is described in adb(1). The adb(1) watchpoint commands :w, :a, and :p enable an integer length (in bytes) to be inserted between the colon and the command character. In mdb(1), the count should be specified after the initial address as a repeat count.
The adb(1) command 123:456w is specified in mdb(1) as 123,456:w.
The /m, /*m, ?m, and ?*m format specifiers are not recognized or supported by mdb(1).