> On Jul 18, 2017, at 11:04 AM, Douglas Taylor via cctalk
> <cctalk@classiccmp.org> wrote:
>
> How does SIMH perform floating point operations for the PDP-11 simulation?
>
> If I run a numerical computation on real PDP-11 hardware and also on Simh how
> do you talk about the comparison?
You can look for yourself: PDP11/pdp11_fp.c. The code clearly implements the
floating point operations the hard way: picking apart the pieces and
manipulating them as needed.
For stuff like this, the devil is always in the details. Some floating point
implementations have odd corner cases that aren't necessarily well documented,
if at all. But it's clear the intent is that SIMH should produce the same
answers as a real PDP-11.
An example of floating point emulation that would be wrong is to convert to
IEEE and operate on "double" values, then convert back. I've done that in the
past as a first stab, but you can't do that if you want the emulation to be
anywhere near accurate.
paul
