Look at PLC 5 1771 I/O, It's still available and has been since the 80s.SLC 500 since the 90s, try and find a 286 passive backplane CPU today.There is no real technical advantage for using MS Windows for GUI work as compared to any other OS.In fact, the GUI used in MS Windows is really not very good, although you can still write a good GUI type program if you work at it enough.However, the last few years it has become remarkably stable.
They are starting to remind me of banks...charging for every little thing. Instead, A-B creates a DISINCENTIVE to move to their hardware.
(Remember when the programmer would count clock cycles to build his timing, and never provide C code for that boat anchor sitting in your warehouse? I have heard about an open source project that programs several PLCs from one GUI and downloads and uploads to several different hardware types.
) Today you could retrofit a junky old PC based dinosour with a sercos card, a kinetix drive, and a few lines of ladder. I even reordered all new cabinets and relays and din rails andpower supplies and kept all the old stuff! If it was ever true I bet AB squashed it like a bug.
The automation industry tends to follow trends in computing, not lead them.
A good example of that is a lot of PLC programming packages required MS-DOS long after MS-DOS had disappeared in the general market.
Those (at least the HTML 5 and Flash ones) tend to make the OS itself irrelevant when it comes to user interaction.