I have a vague recollection of there being a CDC version of a Salford Fortran back in the 1970's. I was a PhD student at Imperial College, and although the main Fortran compiler was 'Minnesota Fortran' (MNF), I'm sure that there was an alternative FTN compiler as well. My memory is decidedly shaky on this, as MNF had better support from the computer centre and it was what I used. I entertained the thought of using FTN because of the graphics support - I certainly read about Heshey fonts which I thought would be useful (and which the DBOS PC version also implemented).
When the PC version came out, it was 386/387 only, and it wouldn't work with all extended memory managers. It wiped the hard disk contents on one computer I used at my University. The DBOS (Dave Bailey Operating System?) DOS extender was powerful, and FTN77 was really fast compared to other compilers of the day, but DOS extenders were a blind alley technically.
I attended a one-day seminar at Salford shortly after ClearWin was launched - in the early 1990's. I think that DB himself was there, and presented part of it. I decided that the complexities of having Clearwin AND DBOS were too much, and I left specific programming for windows alone for a long time. I remember being told that FTN77 was mainly written in Fortran, simplifying setting it up on other computer types - I can't vouch for the truth of that, it may be an 'urban myth'.
The minute that you decide to use ANY extension to a compiler, you are locked in to that one and no other. In my view, Fortran-90 and -95 standards have simply attempted to duplicate (or supplant) existing features of Fortran rather than standardising graphics or useful interfaces (for example to Windows). Those guys on the Standards Committee will never standardise a Windows interface - they mainly use Unix ...
I don't think you will ever get a guaranteed indefinite support for anything. However, it looks likely to me that Win32 programs will work on the majority of PCs for the next decade, even if they are compiled today on XP. ClearWin is rather undervalued by Silverfrost. In my view it is possible to create a very solid commercial program interface with it. It is full of surprises. It could do with rather better instructions, however.
On the subject of speed, the Polyhedron benchmarks don't really show FTN95 in a good light relative to some other compilers. I think that in the main, they are twaddle: I've not the slightest problem with run speeds. FTN95 compiles faster than the others, and has more exhaustive diagnostics. That is more useful to the developer, provided that the run is 'fast enough'.
Eddie