Je n'ai pas trouvé comment visualiser la valeur du registre de contrôle FPU dans VS2012… -_-
Mais après quelques recherches Google, il semble que la valeur qui devrait se trouver dans le registre de contrôle pour une appli .NET devrait être 0x027F. (Y'a pas de raison qu'elle soit différente dans mon cas, sinon il y a un gros souci chez MS )

Ça s'interprète donc visiblement comme :
0x0200 53-bit precision
0x0040 Interrupts disabled
0x0020 Allow inexact precision
0x0010 Allow underflow
0x0008 Allow overflow
0x0004 Allow divide by zero
0x0002 Allow denormals
0x0001 Allow invalid numbers
0x0000 Round to nearest

./18 > Je tire ça de là :

The rounding mode defined in IEC 60559:1989 shall be set by the CLI to “round to the nearest
number,” and neither the CIL nor the class library provide a mechanism for modifying this
setting. Conforming implementations of the CLI need not be resilient to external interference
with this setting. That is, they need not restore the mode prior to performing floating-point
operations, but rather, can rely on it having been set as part of their initialization.
For conversion to integers, the default operation supplied by the CIL is “truncate towards zero”.
Class libraries are supplied to allow floating-point numbers to be converted to integers using any
of the other three traditional operations (round to nearest integer, floor (truncate towards –infinity), ceiling (truncate towards +infinity)).