[zabzonk]

Indeed. Two PhD students came to see me when the polytechnic I worked for switched from a Dec10 to two IBM 4381s.

[them] How can we get our code to work on the IBM?

[me] (examines code) This only looks vaguely like Fortran.

[them] Yes, we used all these wonderful extensions that Digital provides!

[me] (collapse on the floor laughing) (recover) Hmm. Go see Mike (our VAX systems programmer). You may be able to run on our VAXen, but I can't imagine it running on the IBMs without a major rewrite. Had they stuck to F77 there would have been few problems, and I could have helped with them.

Portability is always worth aiming for, even if you don't get all the way there.