A.5.90 FLDCW: Load Floating-Point Control Word
FLDCW mem16 ; D9 /5 [8086,FPU]
FLDCW loads a 16-bit value out of memory and stores it into the FPU
control word (governing things like the rounding mode, the precision,
and the exception masks). See also FSTCW (section A.5.103). If
exceptions are enabled and you don't want to generate one, use FCLEX or
FNCLEX (section A.5.71) before loading the new control word.