PDP-11 floating point exceptions

[utzoo!decvax!ucbvax!unix-wizards]

>From pur-ee!bruner at Berkeley Thu Oct 29 01:34:04 1981
The floating-point processor on the PDP-11's by default only
generates traps for illegal opcodes and divides by zero.  It can
be instructed to trap on overflow, underflow, integer conversion
errors, and use of undefined variables, but by default these
traps are not enabled.  They are, however, trapped out on the
Vax.  This means that programs which bomb out on the Vax with a
floating-point exception will run "successfully" on PDP-11's.

Under the assumption that the abovementioned errors should cause
floating-point exceptions on the PDP-11, I would like to propose
changing the "setd" in the runtime startup code (e.g.
"/lib/crt0.o") to a "ldfps $7600".

P.S.  I haven't seen what 2.8bsd does; our PDP-11's run a
locally-enhanced V7.

--John Bruner