double rounding in x86

[Tom Lynch]

          lynch:
          Actually it is another type of extended, one with an larger exponent
          range, but the same precision as a double.  This is the result of
          setting the precision control     register to double.

  pratt:
  Oops, I'd forgotten that.  In that case I drop the recommendation in
  the message I just sent, that x86 OS's boot up with extended precision
  disabled, since this still doesn't provide double precision arithmetic
  in exact-bit agreement with the rest of the world.

  This would seem to make the x86 for x <= 5 a second class citizen for
  scientific computing.  Anyone happen to know whether this has been
  fixed on the P6?  Maybe someone with a beta-test unit can check this (I
  signed up for one, don't know how they pick people).

lynch:
Yes, and the *horrible part* is that some compilers apparently
store all results to memory and read them back in, in order to
be truely IEEE double compatible.

-tom