The only use of the vax11's pdp11 compatibility
mode that I've ever
heard of was to run RSX-11 binaries under VMS.
I think VMS 1.0 used it because it was not really ready to ship (what a
suprise). The RCS VAXgeek said that some old PDP-11 code was
kludged in with a big hammer (and the compatibilty mode) to get the early
VMS to work. The kludges were dropped shortly afterwards.
William Donzelli
aw288(a)osfn.org