When adding WACCMX modifications, two approaches were taken. One is to modify an existing CAM/WACCM module using 'ifdefs' in the code and the other is to copy a CAM/WACCM module to a separate WACCMX directory and add modifications. There is also a new module (majorsp_diffusion.F90) added as part of the modifications.

With 'ifdefs':

chemistry.F90
dyn_comp.F90
eddy_diff.F90
iondrag.F90
mo_mean_mass.F90
mo_tgcm_ubc.F90
mo_waccm_hrates.F90
nlte_lw.F90
physpkg.F90
radheat.F90
stepon.F90
te_map.F90
tphysac.F90
upper_bc.F90
vertical_diffusion.F90

Without 'ifdefs':

diffusion_solver.F90
dp_coupling.F90
geopotential.F90
gw_drag.F90
molec_diff.F90
physics_types.F90