Bruce Ray on emulating a Point 4 system

From October 14, 2015, to me by email:

The standard Point 4 Mark x instruction set was compatible with the "classic" DG Nova instruction set, and each company added additional instructions over the years.  DG added additional instructions to the "classic" Nova set starting with the Nova 3 and Nova 4 - primarily stack and byte operations.

Peripheral controllers could be program-compatible or divergent, it just depends upon how the computer is configured.  Some Point 4 systems (the Mark 2/3) had some integrated disk/tape/multiplexor peripherals that were total incompatible with anything else, and therefore required special knowledgeable programming.  Other configurations we dealt with used the Lotus 700 series controllers which could be compatible with certain DG disk and tape drives (but had extended capabilities).

EDS/Point 4 created a higher-performance terminal multiplexor that was not DG compatible, but we have also seen Bytronix and CSI (Custom Systems) multiplexors in client systems (and therefore support them in our commercial reNOVAte product).  Of course, "standard" DG-compatible multiplexors could be used in Point 4 systems as well.

So the procedure we use when receiving a client "mystery tape" is to boot the tape and dynamically trace the user program program to determine what device(s) are being accessed.  Then, depending upon the device codes and I/O instructions used (and a bit of our decades of experience with these systems), we can guestimate what controller and disk device is assumed by the user program.

The SimH Nova emulator can emulate some of the possible IRIS configurations, but "it just depends".

Most of the IRIS-similar backup utilities (disk-to-tape-to-disk) were simple sector copy programs, usually the entire disk (or a LU subset).
MCT (MiniComputer Technology), Lotus, and Rianda controllers were popular 3rd-party products in the '70s and '80s.

I have enclosed information for the tape/disk copy programs for your entertainment