Rabbit 2000

Among the Z80 instructions missing in the Rabbit, cpir is particularly notable, since it allows for much more efficient implementations of some often-used standard C functions such as strlen(), strnlen() and memchr().

According to the Rabbit documentation, it executes its instructions 5 times faster[citation needed] than the original Z80 microprocessor, that is, similarly to the Zilog eZ80.

The Rabbit 3000A variant adds a small number of additional instructions for I/O and large integer arithmetic.

There also are the non-free Dynamic C provided by the makers of the Rabbit and the commercial third-party CROSS-C.

The latter two are quite incomplete in their support of the C standard, and their Rabbit 2000 backends are no longer available in current compiler versions.