Identifier name length in g77

Hi All,
Could somebody tell what is the limitation on the length of identifier 
names (functions, variables) in GNU g77 compiler ?
To my knowledge, the Fortran 77 standard limits these names to just six 
characters. On the other hand actual compilers, including g77, permit 
using longer names (which I usually do). Now I'm debugging a piece of 
code in which I used this freedom but encountered some strange 
behaviours and am not sure whether I did not go with identifier names 
lengths to far.

Thank you in advance,

lukasz