RedHat 7.x series in and about 2000 provided a gnu C compiler version 2.9.6 (aka 2.96) that was apparently not authorized by gnu:
http://gcc.gnu.org/gcc-2.96.html
October 6th, 2000
It has come to our attention that some GNU/Linux distributions are currently
shipping with ``GCC 2.96''.
We would like to point out that GCC 2.96 is not a formal GCC release nor will
there ever be such a release. Rather, GCC 2.96 has been the code- name for our
development branch that will eventually become GCC 3.0.
The point being that NEURON will compile without error using gcc2.96 but the results of simulation runs differ from those obtained with other compilers under linux (tested with 3 different gcc versions on 2 different architectures).