I'll assume its this one:
     #options        NO_INSN_EMULATE # CPU does not lack some hardware 
instructions.

Based on this check-in from Ragge:
     Revision 1.71.2.4 / (download) - annotate - [select for diffs] , Mon 
Aug 14 21:11:00 2000 UTC (5 months ago) by ragge
     Branch: netbsd-1-5
     Changes since 1.71.2.3: +3 -2 lines
     Diff to previous 1.71.2.3 (colored) to branchpoint 1.71 (colored)

     Pull up (requested by ragge, approved by thorpej):

     sys/arch/vax/conf/GENERIC 1.76-1.77
     sys/arch/vax/conf/files.vax 1.74-1.75
     sys/arch/vax/vax/intvec.s 1.54-1.55
     sys/arch/vax/vax/unimpl_emul.s -1.2

     This adds emulation code for the POLYD instruction that some VAX CPUs
     are missing. POLYD is used for example in libm.

Its commented out in the GENERIC kernel config that I have, I believe you 
want to build a kernel with it enabled.

No, I can't build you a kernel with this turned on, I'm in california and 
all my VAXen are on a "rolling blackout" :-(

--Chuck

At 09:14 AM 1/18/01 +0100, NetBSD mailing list wrote:
>Hi,
>what is the specific Kernel option to enable the emulation ??
>May I know it ?
>thanks
>
>Rick
>
>On Wed, 17 Jan 2001, Brian Chase wrote:
>
> > On Wed, 17 Jan 2001, Chuck McManis wrote:
> >
> > > Actually Rick is referring to the POLYD instruction that isn't present on
> > > the 4000/60 and 4000/90 and so has to be emulated. If you haven't
> > > configured your kernel to emulate this instruction you get an illegal
> > > instruction trap when you try to execute FP code in some apps.
> >
> > Ahh.. my bad.
> >
> > -brian.
> > --- Brian Chase | bdc@world.std.com | http://world.std.com/~bdc/ -----
> >       Are you absolutely sure that you want to do this? [ny] y
> >
> >